"What are some important, but uncomfortable truths that many people learn when transitioning into adulthood?"

This long list needs a post scriptum: Very few people manage to accomplish this transition :-/

Certain people -- some of whom are in positions of enormous power -- just do not give a damn about other human beings. A certain head of state in Syria comes to mind.

I'd also say that your ability to care about other people, along with overall sanity, will diminish under constant stress. That's why "Preserve own sanity" is #1 on my rules to be followed in case of sudden world domination list and something I need to stay aware of even in my current (and normally not that stressful or important) job.

I'll try to reframe those that hit me the hardest

• One day we will all die, and 999 out of 1,000 people will be remembered by nobody on earth within a hundred years of that date.

The duration of our relevance to others is just one of many dimensions of relevance. And, does the duration of the meaningful experience have diminishing returns?

• Practically all of the best opportunities (in business, in romance, etc) are only offered to people who already have more than they need.

In absolute terms, yes, but in relative terms, that's irrelevant except that increasing inequality increases the opportunity for exploitation. And, awareness of inequality as a health problems appears to be bigger than I expected before engaging with the peripheral academic literature.

• The idea that you will be happy after you make X amount of dollars is almost certainly an illusion.

This is empirical untrue. See 80,000 Hours article on money and happiness. You will be happy(ier) after 50k ;) among other factors.

• The idea that you will be happy after you meet [some amazing person] is almost certainly an illusion.

the PERMA model of positive psychology suggests relationships are critical for happiness. And, personality factors which are distributed among populations are important to successful relationships. Plus, prespecified wants in a partner best correlate with relationship satisfaction. Additionally, positive illusions about partners are one of the best predictors of relationship success anyway.

• For most people, death is pretty messy and uncomfortable.

Discomfort doesn't have to be distressful, it can be eustressful. Same with mess.

• When you don't possess leverage (go look up "BATNA"), people will take advantage of you, whether they mean to or not.

But not everyone will. You can select your social circle (or at least, most people reading thing can) to choose those who are normatively non-exploitative. Make friends with deontologists!

• Almost everybody is making it up as they go along. Also, many (most?) people are incompetent at their jobs.

This inefficiency provides the opportunity for improvement :)

• When talking about their background and accomplishments, almost everybody is continually overstating their abilities, impact, relevance, and contributions.

I hope that's indicative of a high self esteem

• Physical beauty decays.

Helping people realise the importance of other kinds of beauty, for self worth reasons.

• Compared to others, certain ethnicities and races (and genders, and sexual orientations, and so on) are just plain royally f*cked from the day they're born.

As a non-white, I think the author is royally fucked thinking that things can't and aren't changing. Fuck you're white supremacy.

• Very few people will ever give you 100% candid, honest feedback.

Not if you take things so negatively, like you clearly are Mr. Author.

• People are constantly making enormous life decisions (marriage, children, etc) for all of the wrong reasons.

Who are you to judge the wrongness of their decision?

• Certain people -- some of whom are in positions of enormous power -- just do not give a damn about other human beings. A certain head of state in Syria comes to mind.

You can't read their minds and intentions

• Often, the most important and consequential moments of our lives (chance encounter, fatal car accident, etc) happen completely at random and seemingly for no good reason.

I feel few rationalists would think this way

• Your sense of habitating a fully integrated reality is an illusion, and a privilege. Take the wrong drug, suffer a head injury, or somehow trigger a latent psychotic condition like schizophrenia -- and your grip on reality can be severed in an instant. Forever.

Reading this really stung me. This has been a really important concept in my life. I've taken the wrong drug, suffer some sort of cognitive disorder, unspecified, but not due to any head trauma from brain scans, and at various times have been given given psychotic diagnoses (later retracted). Living in a fully integrated reality really is a privellage. I'm grateful for what grip I have on it right now as I write, which is better than it has been when I've been a little psychotic. But, it's not a clear linear descent into hell. As psychosis worsens it goes hand in hand with a flattening of affect and worse insight. And, as insight increases, depression is seen to increase from both personal and academic experience. Really the descent out of reality is the worse part, and moments of insight, rather than a lifetime of misery. I am happy usually, not right now, but that's why I decided to write a long-form response - to improve my mood. And sure, taking the wrong drug has one at least one occasion distorted my sense of time enough for it to feel like forever in hell, but you know what, that's not right now. So I mean...at least it's not eternity? I really hope someone can help me flesh out a more positive reframe than this.

Edit: To this I can also refer you to the weakness of strength. My pain sacrificially broadens the minds of others to be grateful for their sanity.

Thank you for sharing this James_Miller and author Patrick Mathieson.