If you assume other people are the same as you along every dimension then you will overestimate other people exactly as much as you underestimate them. It is a good first-order approximation to assume other people are like yourself.
Most people are in the middle of any given bell curve. You are probably in the middle of any given bell curve too. It is a good second-order approximation to assume other people are like yourself.
But…if you assume you are statistically normal when you are not then you will have problems. I have made this mistake many, many times because my personality is extremized in three big ways.
I once heard a friend, upon his first use of modafinil, wonder aloud if the way they felt on that stimulant was the way Elon Musk felt all the time. That tied a lot of things together for me, gave me an intuitive understanding of what it might “feel like from the inside” to be Elon Musk. And it gave me a good tool to discuss biological variation with. Most of us agree that people on stimulants can perform in ways it’s difficult for people off stimulants to match. Most of us agree that there’s nothing magical about stimulants, just changes to the levels of dopamine, histamine, norepinephrine et cetera in the brain. And most of us agree there’s a lot of natural variation in these chemicals anyway. So “me on stimulants is that guy’s normal” seems like a good way of cutting through some of the philosophical difficulties around this issue.
― The Parable of the Talents by Scott Anderson
According to drugabuse.com, amphetamines have the following short-term effects:
These characteristics describe my baseline state. I feel like I am on stimulants all the time. Natural amphetamines have advantages. I am energetic. I concentrate well. I get lots of work done.
They have disadvantages too. Amphetamines are associated with headaches, appetite suppression, severe anxiety and obsessive behavior all of which also describe me. The headaches are ignorable because I cannot remember ever not having a headache. The appetite suppression is survivable because I live in a civilization full of convenient calories. The obsessive behavior is a double-edge sword. On the one hand it makes me bad at small talk. On the other hand it helps me finish things.
The anxiety in causes me to overprepare for disaster. When your are anxious, it is natural to search for a threat. When I feel merely moderate anxiety I ought always to consider that there may be nothing to fear but the fear itself.
I should assume a prior expectation that other people have the following characteristics relative to myself:
Among the Big Five personality traits, curiosity (openness to experience) is my most extremized one.
Other people are comparatively closed to experience. They are conventional and traditional in their outlook and behavior, with familiar routines and a narrow range of interest. I am extraordinary, with a wide range of interests and no set routine.
Openness to experience is considered a positive trait within liberal Western society, but it comes with disadvantages. I suffer hard for my nonconformity, think in peculiar ways and tend to get absorbed by my own fantasies.
When I meet new people, I ought to assume the following characteristics as a prior:
The empathizing–systemizing theory suggests there is an evolutionary tradeoff between empathizing and systematizing with autism at one end and schizophrenia at the other end, with most people in the middle. I find it a useful model for understanding a difference between myself and others. I am heavily on the systematizing end of this spectrum.
There is less research on this topic than the others so instead of listing the traits of systematizers I will list the traits of autistic people and flip them around. Compared to me, other people are:
Comparatively-speaking, I am a heretical savant high on cocaine. That would explain why strangers tend to remember having met me. I can improve my interactions with others by adopting the prior that they are passive parochial team players.
High openness is associated with a preference for frequently-changing schedules. Systematizing is associated with schedule inflexibility. How can I exhibit both traits? I am inflexible toward others when it comes to my whimsical schedule.
By a similar paradox, I feel comfortable in the traditional oppressive culture of Japan. My systematizing proclivities enjoy the quiet perfectionism. Meanwhile, as a foreigner, I am not myself expected to conform.
My extremized characteristics all contribute to my advanced technical skills; I am pathalogically good at writing software. Ironically, the same traits simultaneously make it harder to find a job and fit into a corporation. I can only work somewhere where my technical skills are sufficiently valued for the company to tolerate my eccentricity. My ideal company would probably be working remotely for a small machine learning team. Or I could simply self-employ.
Socially, these extremized traits suggest I might connect well to other people through art, which benefits from obsessively systematic nonconformity. In particular, I might have exactly the right character sheet to write a technical webcomic.
These traits also suggest I should be careful with theoretical physics as it were a dangerous prescription drug.
 Disclaimer: I have never personally taken amphetamines, cocaine, heroin, meth or anything along those lines. I apologize for my lack of empirical rigor in this domain. ↩
 Thesaurus.com lists these words as antonyms to "obsessive". ↩
 My other Big Five personality traits fall in the middle 98% of the bell curve. ↩
 Thesaurus.com lists "extraordinary" as an antonym to "traditional". ↩