What is the main problem I found in my 20s trying to stay alive here on earth?

 Unrealistic expectations.

They come in many different varieties.

For example, I met many people knowing that they wanted to be Doctors, Lawyers, accountants etc. only to find out that they actually HATED this trade once they learned it. So, not only had they wasted their time learning this trade for 6 or 7 years or more they often hadn't started relationships to create families and so by 30 this is often too late for people to start. 

For example, I started dating at age 15 mostly because President Kennedy had gotten assassinated. So, I was always ahead of the game for getting married and starting a family. In fact, I tried to drop out of High school in my senior Year because I had been dating a girl 21 years old when I was 16 years old. So, I was always ahead of the dating game and the moving towards getting married and having children game.

However, I have met so many people who knew for sure what they wanted to be then went to college to become that and then were miserable with their trades they studied for and then they were 30 or more and couldn't learn how to date to meet "The right person".

However, it's also true that I was married 3 times because my life choices weren't perfect either.

However, for some reason I feel the most sorry for people who studied 6 or 7 years then had 100,000 dollars in student loans to pay back and then hated the trade that they had chosen and then either never married or hated the person that they were left with because they didn't date enough people before hand to understand what they really needed and wanted in a mate.

So, what is the main problem with ones 20s?

UNREALISTIC EXPECTATIONS THAT ALMOST ALWAYS MAKE PEOPLE MISERABLE (AND SOMETIMES MISERABLE ENOUGH TO STOP LIVING AT ALL.

So, what is the solution?

I don't think there is any one solution. 

However, I found with myself I couldn't make plans that worked in regard to college in regard to a trade.

What I did realize was that I needed to become a complete opportunist simply because I didn't do well at all with disappointment.

So, since Disappointment almost caused my death between ages 21 and 25 many times becoming an opportunist was the only way I saw to survive at all.

Also, studying psychology, philosophy, Anthropology helped me more in college than anything else I ever studied. So, even though computer science and computer programming was my first major in college it wasn't going to psychologically keep me alive past 25. In order to really stay alive philosophy then psychology then Anthropology actually taught me more about WHY I wanted to stay alive for myself and my children and for all life in general.

So, life isn't what I believed it to be AT ALL before I went to college.

You cannot fit yourself as a square peg into a round hole or vice versa.

You need to create the world for yourself in your own image. Otherwise you might not be alive tomorrow or ever.

So, create your own world to live in that works for you. Otherwise you might be gone in a few years.

This is what my life experience taught me along the way. And I'm almost 77 years old now.