Memory Repository 🧠

@MemoryRepository | Pharmacy Student 💊 Digital Garden | Productivity | Studying | Writing | PKM | Life | I deposit bits of knowledge, learnings and memories into this memory repository.

How to stick to a habit

Reading time: 3 min

How to stick to a habit (and Operant Conditioning)

In addition to ways of preventing ourselves from dropping habits (removing disincentives), what is an effective way of building and sticking to a habit (adding incentives)?

I started to workout as I want to be healthier. I also have the following conditions:

  • My time is limited and I don't want to commit time to working out
  • A workout is inherently tiring and an upfront cost for uncertain future benefit
  • Watching videos is a joy I like to indulge in
  • Despite my 'lack of time' (or rather differing priorities), I'm happy paying a bit of time every day to watch videos
  • I am aware that watching videos for entertainment is generally unproductive past a certain point
  • I consider working out to be something productive

To solve all of these problems, I combined my video watching time with my workout time (I don't see a reason they have to be separated if my workout is indoors and I'm not bouncing all over the place).


  1. Combines a rewarding activity with a punishing activity (immediately, anyway)
  2. I'm not expending extra time
  3. I'm converting an 'unproductive' activity into a combination 'productive' activity.

And this is working! I've found working out to be a joy, probably because I'm happy watching videos while doing it (along with happiness chemicals released while working out). Especially since I know I'm not spending any extra time to do this.

I'd recommend this to anyone trying to form a habit that involves an up-front unpleasant action (such as working out):

Tie a pleasant habit with the new unpleasant habit. Preferably, perform the habits simultaneously (see below).

What I described above can be framed in the operant conditioning process, generally attributed to psychologist B. F. Skinner.

It describes how our behaviours are changed by reinforcement (reward) or punishment, respectively increasing or decreasing the likelihood of continuing the behaviour. Each reinforcement or punishment activity can be further divided into positive or negative, such that there are 4 categories:

  • Positive reinforcement: adding a reward
  • Negative reinforcement: removing a punishment
  • Positive punishment: adding a punishment
  • Negative punishment: removing a reward

The methods I described to avoid dropping habits are arguably negative reinforcement- I take away something negative (by reducing commitment/friction) to make the habit less of a chore, to encourage the habit.

The methods I described in this post entail positive reinforcement- I add a reward that comes with the habit.

Placing a reward with a habit is arguably better than placing a reward that comes after the habit, given that we are generally 'present-biased'. This means that our current priorities and feelings take precedent over our future priorities and feelings. As such, if the reward comes after the habit, my present self has to pay the immediate price, and only my future self will get the reward. The cost facing my present self takes priority over the future reward, making the reward less effective. This is not an issue if the reward comes along with the habit, simultaneously.

Write publicly for well-researched and thought-out writing

Reading time: 3.5 min

Response to The Importance of externalizing your thoughts by Permafrost🧊Yard (@Yard)

That piece primarily details the limits of working memory, and writing (publicly) as a way to overcome this and produce better thinking.

"It forces you to research intensively about the subject and to also explain it coherently, but it also exposes you to the feedback people might give to you, allowing you to see your possible mistakes, to get better at the subject, and to improve your technical writing skills."

I entirely agree with the notion of public writing forcing you to do extensive research on the topic and exposes it to feedback.

In preparation for some of my longer, essay-type pieces, I researched extensively to ensure that I have a reasonably good grasp of what I am talking about, if there is supporting evidence, and what potential flaws there are in the evidence. Examples include:

The power of free and detriment of loss aversion, where I carefully researched the topic and looked through the study I detailed.

Role of QR Codes Entailing Genetic Tests and Medical Records, where I looked into the role of DNA in modern medicine to consolidate my existing knowledge and find more specific examples.

Do non-iron clothing cause cancer?, where to stick to medical ethics and the idea of 'do no harm', I made sure to extensively research the chemical, professional recommendations, and existing studies into how the chemical affects humans.

Human Longevity, where to support my existing knowledge, I researched potential evidence that contradicts the original post I was responding to.

The common pattern between these posts is that I am making a claim, and attempting to support it with convincing evidence and non-one-off real life examples, rather than purely sharing my own thoughts and experience.

Another common thing is that these can be relatively complicated topics, and as such require a long time to write to ensure coherence, and ensure the reader understands the point the author is trying to make, and prevent misinterpretation.

My main motivation in doing so much preparation is to avoid writing misinformative garbage when discussing what I consider to be serious topics.* I hope to catch possible mistakes in my points before it becomes public, such that it can bring value to readers and further feedback would genuinely improve the thinking and writing.

As such, writing publicly indeed seems to have the benefit of forcing one to properly research the topic and be coherent, at least on serious topics. I naturally did these things when writing the above pieces. I reckon this is an excellent way of producing better work.

Also, I just realised the relevance of this comment to my prior post (The power of free and detriment of loss aversion, see above):

"Life is a constant battle between you and bad luck. We are supposed to make sacrifices to increase the probability that good things happen. But this is difficult, you not only have to deal with difficult situations but also with a lot of distractions that might seduce you to avoid what you have to do."

Indeed. We have to put in our time, effort, and other resources and hope our endeavor results in a success, with the risk of losing it all in failure. One reason this is difficult is our loss aversion.

Asterisk, afterthought:
*I wonder how that applies when it comes to modern journalism. Does writing publicly incentivise well-researched writing and accountability in that environment? If not, why the difference?

Certainly, committing publicly brings motivation to stick to your commitments. See examples 1 (learning to code) and 2 (100 days writing challenge).

The power of free and detriment of loss aversion

Reading time: 2 min

What is the power of free?

If you were offered, for free, a single Lindt Truffle (a round chocolate shell with soft chocolate truffle filling inside) versus a single Hershey's Kiss (a smaller, harder chocolate), which would you choose?

If you are familiar with both chocolates, you would most likely choose the Lindt Truffle. Most would consider a Lindt Truffle to be of higher value than a Hershey's kiss.

In an experiment (see Shampanier et al., 2007), when given the option between these chocolates, at the given price:

Lindt Truffle ($0.14) or Hershey's Kiss ($0.01)

Significantly more people chose Lindt Truffles over Hershey's Kiss.

However, when the cost of both were decreased equally by $0.01:

Lindt Truffle ($0.13) or Hershey's Kiss (free)

Significantly more people chose Hershey's kiss over Lindt Truffles.

Despite the difference in cost staying the same, such that the cost-benefit difference between a Lindt Truffle and Hershey's kiss theoretically staying equal, people's preference switched to the free option.

This is irrational- in the subject's thought process, the value of Hershey's Kiss must have increased purely because it became free. As such, something that becomes risk-free due to becoming free not only decreases cost, but apparently gets an increase in value as well. This is related to how humans are generally loss averse- we hate losing value.

For example, we generally view losing $0.05 as a greater loss in satisfaction (or simply happiness) than the satisfaction we would gain from getting $0.05 (see Prospect Theory). As such, we prefer to avoid loss at all costs, even if our lower-risk option makes us produce suboptimal results.

Source. Loss of $0.05 results in a much greater value loss than the gain from getting $0.05.

This puts us at odds with the idea of maximising your 'luck' via going for as many opportunities as possible. We would prefer to avoid opportunities just because of the risk of loss involved (risk of failure).

By becoming aware of our intrinsic loss aversion mindset, we can become more accepting of the risk associated with taking more opportunities in life, and become more willing to put ourselves out there to maximise our surface area for luck to flourish.

Kahneman, D., & Tversky, A. (1979). Prospect Theory: An Analysis of Decision under Risk. Econometrica, 47(2), 263–291. https://doi.org/10.2307/1914185

Shampanier, K., Mazar, N., & Ariely, D. (2007). Zero as a Special Price: The True Value of Free Products. Marketing Science, 26(6), 742–757. https://doi.org/10.1287/mksc.1060.0254

An interesting book detailing more cases like this: Predictably Irrational by Dan Ariely.

"Who am I?" - A question to ask for long-term planning

Reading time: 1.5 min

In our childhood, we explore our own identity. Our guardians, peers and education guide us towards asking ourselves what we are and who we are.

After taking my final class today before exams and clinical rotations begin, I asked myself:

"Who am I?"

That's a good signal for me to do tertilely year planning again. To look at what I've achieved in the past few months, review my existing goals and commitments, and to plan for the coming future.

With any big transition, it's a good opportunity to explore how far we've come and how we've changed as time passed.

Going back to the questions we asked ourselves as children, asking ourselves who we are now, and what we want to become is a good way of doing any moderate to long term review (monthly, quarterly, tertilely, yearly). It allows us to evaluate the gap between our past and current self, the gap between our current and future self, and naturally, what we have to do in order to achieve what we want for our future self.

Writing as a way to de-stress

Reading time: 2 min

I find that I gravitate towards writing for my digital garden at late nights whenever I feel excessive stress. This has been the case for recent writings here.

Specifically, I write about interesting thoughts and ideas, unrelated to study or work, rather than 'concerning thoughts' and tasks plaguing my short term memory (which are generally related to study or work).

I really wanted to reflect on why this is the case.

It's not necessarily about emptying unnecessary information from my mind. Rather, it feels good to simply think about something else for a while, something unrelated to things I've been constantly working on for that period in time.

Perhaps writing is something that allows one to detach from day to day stressors, just for a little while. Writing allows us to engage with our useful and interesting thinking while allowing us to detach ourselves from our immediate environment and our normal stream of random, cluttered, nagging thoughts.

Writing this piece certainly brought me calm and joy.

I would implore others to try writing about their shower thoughts* and other stuff that interests them whenever they feel excessive stress. You might surprise yourself with the good writing you come up with and the relaxing time that comes with it.

Or maybe it's because I just enjoy writing here and thinking about these topics?

*This was another piece written while I was in the shower (or at least largely thought out in the shower). Shower thoughts are brilliant but can be difficult to capture.

It's so easy to keep scrolling on social media

Reading time: 3 min

Read @Brandon, The Effect of Social Media on Blogging

Interesting read. The post mentions how users of social media are unlikely to regularly visit external links (a blog), if one stops linking to the external website in their social media posts.

I think there are a few factors involved:

  1. People do not like to move off the platform they are currently using, and social media platforms are designed to be that way.
    Social media platforms are designed with the intention of maximising retention and attention time- the platform discourages users from moving off their site, even for just a brief while to visit an external link. The friction involved from context switching and otherwise actions required to navigate to and through a different platform is much greater than just simply scrolling for more content.

  2. Social media gives a method for people to easily engage.
    Buttons for reactions, comments, and replies are right next to the main content, making it very easy to engage. This also plays into the above point, where ease of access reduces the friction of engagement, and hence make it easy for people to express their resonance with or otherwise reactions to content.

  3. Social media will actively suggest posts to people in a 'grouped' environment, whereas blogs and websites are 'siloed'.
    Everything on social media is compiled into a neat stream of content for a user to scroll through, whereas blogs and other websites requires the user to go to that particular website, and move between each post with clicks- this is friction. This links back to point 1- users will likely continue scrolling. Even simply creating an RSS feed, although achieving a similar purpose, requires more time and actions than simply clicking/tapping on a "follow" button.

  4. People on different platforms have different preferences for content length.
    Perhaps those visiting or peeking in via social media only want a short summary or sharing, or are at least familiar with short content (given the short word/character limits on some platforms). This would likely be the case for Instagram and Twitter. Longer, more extensive content, although perhaps of better quality, might not fit the preference of those on such platforms.

We live in a time where there is so much content and resources available that it is impossible to look through everything, given our limited time and attention. It's wonderful that information is so readily accessible, but we now have to be selective on what we choose to consume. Social media platforms are designed with this in mind. They capture you (and make you spend your time and attention there) by making interaction with the platform almost effortless (besides scrolling). This lack of friction and efforts to make you accustomto the platform disincentivises people from exploring further, outside of the platform they regularly visit.

Further thoughts:

  • Combined with personalised content matching and recommendations, this creates an echo chamber

Is Ego Depletion Real?

Reading time: 2 min

I happened to write about ego depletion and did some quick research to clarify my knowledge of this concept, and found that more recent studies have indicated that there is no evidence to support this effect.

Ego depletion is the reduction in willpower or ability to make decisions or exert self-control after every time you do so. It's a limited source, but recovers over time.

The phenomenon I noted here on too many choices for the same type of product in supermarkets decreasing sales figures is explained by this theory. Exerting too much 'decision-making ability' makes us not want to make further product decisions.

This is also used to explain why we (or at least I) get so (mentally) tired after shopping for clothes- my ability to make further decisions and exert self-control has completely run out.

A more recent, massive study (over 3,500 subjects) with sound methodology and statistical methods has indicated that there is a much higher chance that there is NO evidence for ego depletion than evidence FOR ego depletion.

A plausible explanation given from this source is that the mountain of prior studies supporting the idea of ego depletion were either analysed with questionable statistical methods (increasing the likelihood of false positive), or negatives were explained away, while positives were considered to be contributing to the idea of ego depletion.

Well, this throws a thorn in what I was writing about. Oh well, I learned something new today and it changed my view of ego depletion from 'true' to just 'plausible/inconclusive'.

Oh yeah. Made it to Day 7 of 100 days of coding for Python. Slow but steady.




The Hedonic Treadmill - Why we can never be constantly happier

Reading time: 2-3 min

Throughout quite a few of my posts, I explored ways in which we can increase our happiness. I recently came by a notable theory, relevant to happiness.

The Hedonic Treadmill

The "hedonic treadmill", coined by Brickman and Campbell (1971) describes how humans rapidly return to a 'baseline' state of happiness, even after significant positive or negative events.

This is illustrated by two examples by this source (Oxford Reference), on winning the lottery and accident victims:

"In a classic article in the Journal of Personality and Social Psychology (1978), Brickman and two colleagues provided evidence showing that, a short while after the events that changed their lives, lottery winners are not substantially happier, and accident victims who have become paraplegic are not substantially less happy, than other people."

Significance to prior posts

This could explain something I described in this post.

"But by the time our future selves experience this supposed stepped-up happiness or success, we desire more. Our achievements only ever give us fleeting happiness and fulfilment. Eventually, the delight from achieving what we desired will fade and further goals will be set."

The happiness we gain from recent achievements are quickly lost, and we return to a baseline state of happiness, and then we desire more. This produces an endless cycle of pursuing happiness, and wanting 'more' in our lives.

I wonder how this observation affects an argument I noted here, on how removing all negative memories may possibly remove the contrast between happy and sad times. If we, by default, quickly re-enter a neutral state of happiness regardless of recent happy or sad events, does this 'contrast' argument still stand?

More mentions of this phenomenon:

Current Commitments and Future Satisfaction

Further thoughts:

As noted here, I once came by this claim of

"...consistent gratitude will raise happiness to the same degree of doubling income."

(Although I never found a source for it.)

Does gratitude increase our happiness by a consistent amount above our baseline as long as we persist with administering gratitude in our life, or does it cause a temporary increase, and then our happiness gradually or rapidly falls back to baseline soon after?

Also, I made it past 100 days of code day 4. Slow, but progress is progress.

Making commitments publicly for accountability and for like-minded people to join you - 100 Days Of Code (kind of)

Reading time: 1 min

100 days of code (kind of) to learn Python

I started the 100 days of code challenge for python 3 days ago. Currently on day 3.

Python is something I wanted to learn for a long time as I think it'll be useful in the future, but I never seriously got past beginner syntax or found applications for it.

Now, I found something I can follow along to start building up my skills. I don't think I can strictly commit to 1 hour every single day, but a few minutes every single day or a few hours a week is definitely something doable. I've proven this to myself in the past two months, taking an extra online course on pharmaceutical drug development for hours each week.

Why commit publicly?

I think committing to things publicly will give some degree of accountability to a commitment. Certainly more than just a purely self-enforced "I'll do it" commitment. At least progress, a timeline, and your reflections along the way can be visibly seen on a public record.

It's also a good way to reduce the feeling of going alone on a journey. There'll be others also doing a similar challenge and hoping to find others on the way. Perhaps there'll be someone in the same position I was in (wanted to learn but never got started or never figured out where to start), and this might give them the push they need.

Also, thank you whoever commented on my guestbook. Really makes my day. :)

Role of QR Codes Entailing Genetic Tests and Medical Records

Reading time: 3-4 mins

Response to @MindThink, 'What If -> The Pandemic is a Distraction?'

It's been a while since I visited Listed.to. This is my 100th non-unlinked post, I believe.

I happened to read this post about assigning unique QR codes to every single person for mass tracking, with the examples listed being "medical records, bank account, shopping information, DNA".

As someone with specialised knowledge in health and healthcare, I want to comment on medical records and DNA in particular.


Having medical records and (pharmaco-)genetic test results as a QR code that you can choose to present to your healthcare provider is not necessarily a bad idea.

I understand that this can be a slippery slope with implications in privacy, personal choice, and surveillance. But there are legitimate reasons this can be beneficial to individuals.

I will give a case where such a system will bring benefits to healthcare.

Example 1: Codeine Metabolism and Dose

For example, each of us metabolise (deactivate or activate, depending on the drug) the medications we take into our bodies at a different rate (speed), depending on our genetic code.

As a result, the same medication dose can work vastly differently in different people- a person who metabolises a particular medicine quickly might experience no therapeutic effect due to their body breaking the drug molecule down too quickly, before it reaches a high enough concentration in our body to take effect clinically. A person who metabolises a particular medicine very slowly might experience toxicity (overdose side effects) with the same dose.

This is negligible for most over-the-counter medicines, but may be significant for prescription medicines.

Codeine is a good, well-established example of this. It's a painkiller, but is metabolised (activated) in our bodies into stronger compounds (including morphine, a much stronger painkiller). The CYP2D6 gene can vary (exhibit polymorphism) among different individuals, resulting in differents extents of codeine activation in different individuals. Someone who is genetically a poor metaboliser (poor activator) of codeine might get little to no painkilling effect. Someone who is genetically a rapid metaboliser (rapid activator) might overdose from typical codeine doses, resulting in morphine toxicity (bringing severe consequences, including death).

Example 2: Talazoparib and Breast Cancer Cell Susceptibility

Aside from metabolism and dose considerations, genetic testing can also determine whether particular medicines work for your condition.

Breast cancer, is a disease where therapy options have advanced far over the past two centuries. From surgical removal, to radiation, to less invasive surgery, to the first drugs, to the first targeted therapy options (specifically targets cancer cells), to now genetic testing to identify which type of drug or biologic (combination) works best against a particular individual's breast cancer.

Talazoparib (brand name Talzenna) is a drug that requires genetic testing to show that the patient has one or more particular breast cancer gene mutations (BRCA1 and/or BRCA2). Breast cancer cells with such mutations are susceptible to the action of this drug.


I haven't specifically touched on the importance of medical records and medical history as they were not the intended focus of this piece, but they are implicated in drug-drug interactions, drug allergies, etc., things that can be either negligible or life-threatening depending on the drug. Either way...

Instead of having each healthcare provider you come across run a pharmacogenetic test on you (for your own medicine safety), wasting precious and limited time and human/monetary/environmental resources, the patient could choose instead to provide a QR code that provides their verified genetic data and medical records to the healthcare provider, to allow for easier, safe prescription of a particular medicine.

How one accomplishes this in a private and secure manner is another issue, one which I am not an expert on. However, I'm confident that if implemented with privacy by design, such a system can bring benefits to many around the world.








NFTs and blockchains for vaccines

Work off a calendar for efficient work

Reading time: 1 min

I saw a video arguing how high-level, efficient work surrounds working off a calendar rather than a to-do list.

While I didn't see the specifics of what exactly was on the calendar, an educated guess leads me to think that they are all tasks. The person in the video time blocked his entire week out, assigning a task into every available free work hour of the day.

I do this via a non-calendar app (Sorted 3) when I have a ton of work waiting for me and limited time or when I feel completely overburdened (and/or my main task manager (Things 3) is failing me due to having too many tasks and insufficient time spent organising).

Perhaps I should try out this method for the next month and a half. I do want to get back to efficient work.

Spreading your goals and priorities too far apart, and next theme: Laser Focus

Reading time: 2 min

Well, the results for academic results came out and I did not get the outcome I wanted. Even though it wasn't unexpected.

In such cases, which ask: Why? What factors contributed to this outcome?

After reflecting on the outcome of every single course, both the strong and weak performers, my answer this time around was:

I worked on my assignments and other goals and commitments every day rather than studying every day. Many of these other commitments do align with the ideals of my present and future self. Yet, I've spread my goals and priorities too far apart, and these other priorities became detrimental to my academic priorities.

Now, I've sufficiently met enough of my other goals such that I am satisfied. It's now time to converge and focus. To exceed at a particular goal, we must be laser focused on achieving that goal.

Therefore, my theme for the next tertile of the year will be:

Laser Focus. (On academics).

To start cutting out commitments and focus on my now-main goal and priority, my academic results. A lot of other good things happened this year and a lot of other goals have been met this year but now, this takes priority.

Motivation to myself:
I've done it before. I've achieved the exact result I need now just a year and a half ago. I can do it.

To future self:
Role of imagination/framing on achievement?

Do you have a moment to talk about our lord and savior, Anki (and consistency)?

Out Of The Quarantine 8: Isolation Encourages Creativity Tasks?

Reading time: 1 min

I've been focusing on rest and creative projects in quarantine. I did some designing and publishing in addition to resting and playing games, while putting off mindless tasks during my time in isolation

Out of quarantine, I focused on 'life admin' tasks (getting my life back in order in the real world outside of my quarantine room) and menial writing assignments. Stuff that does not require too much creativity.

Interesting. I can't tell if isolation encourages creativity tasks or this is pure coincidence. I wonder if it has something to do with my brain needing more stimulating when there was insufficient stimulation in my quarantine room and therefore I do a lot more thinking and idea/art generation than when I have more stimulation in the outside world.

Out Of The Quarantine 7: UV Light Exposure and Ageing

Reading time: 1 min

When we expose ourselves to sunlight, we expose ourselves to ultraviolet (UV) radiation.

Prolonged exposure to UV exposure induces skin wrinkling and skin cancer, arguably signs of accelerated ageing (by DNA damage).

UV radiation damages our DNA, accelerating ageing via the DNA damage theory of ageing, where over time, alterations to our DNA accumulate to the point where we either experience ageing, or that our DNA is sufficiently damage so that our DNA repair mechanisms do not function well enough to have slow, normal ageing.

Because our DNA accumulates damage every day, our genome can be used to identify how long we've been born. This is the epigenetic clock.

Wear sunscreen, clothing and minimise sun exposure. Unless you reside in a place/live a life with too little exposure resulting in a deficiency in vitamin D, in which case consider some sunlight every day (a good 20 minutes is reasonable) and supplements. (This vitamin is important for our immune system. For example, vitamin D deficiency is linked to atopic dermatitis, aka eczema).

Further reading: Review article, Atopic dermatitis and vitamin D: facts and controversies*

There are studies that show a positive and inverse correlation between vitamin D deficiency and atopic dermatitis. However, the author of the review does caution about other factors that may lead to the inverse correlation. More evidence does seem to point towards deficiency is linked to atopic diseases.

In The Quarantine 6: Conscious forgetting

Reading time: 2 min

Following up on this (In The Quarantine 5: Would you delete haunting memories?).

I talked about a "what-if" scenario for deleting memories.

On further reflection, it's not as far fetched as it might seem. For almost all of us, memory is fleeting. It's lossy and details change every time we recall it. (Every time we recall a memory, we're recalling our most recent recollection of the memory, not the first, original impression of the memory itself (or at least I remember reading around two years ago)). Most of the things we encounter are forgotten very quickly (see the forgetting curve).

Yet, why is it that some memories are hard to forget, including those that give us significant grief or otherwise sadness?

"Active recall" is a highly effective study method if you want to commit something to your long-term memory. It's the act of recalling what you want to remember, from memory. Whenever we think about (or actively recall) the memory that resulted in negative emotions, we strengthen the connections in our brain (to some extent physically and chemically), imprinting the memory in our minds more strongly.

One strategy I use to forget things (e.g. if I'm asked to or I want to) is to consciously not think about it. By consciously avoiding the topic, not letting your monkey brain reading out topic, and not specifically recalling any of the details of the event, it is possible to slowly, over time, weaken the connections in your brain sufficiently to specifically and consciously forget things.

Not letting your inner voice read out the topic (e.g. by immediately thinking about something else or emptying your mind) is important as this prevents you from recalling the topic when you're consciously avoiding the topic/details.

I say "in the" quarantine. Not really anymore. I'm free.

In The Quarantine 5: Would you delete haunting memories?

Reading time: 1 min

If we could remove memories from our mind, would you or should you remove the saddest memories that repeatedly haunt you?

I thought about this for a while today and could not come to a sound answer. To an extent, I really want to say yes, I would want a particular memory to be deleted as it causes me a lot of recurrent grief and sadness.

However, we also lose the lessons learned as a result of the resolutions or outcomes from the event. Another consideration (not sure whether I agree or not though) is the argument of losing the 'contrast' between happy and sad times.

Could we still feel happiness (or at least relative happiness?) if we deleted all semblance of negative memories? I would like to say yes, although I cannot quantify this or back it up with evidence. Maybe there is sound research done on this as of current time that I am unaware of.

Although, does the contrast argument stand? See:

The Hedonic Treadmill - Why we can never be constantly happier