Difficult and useful things people have to learn in their 20s?

Don’t waste your time. Time and health are the most valuable assets you have, use them the right way or you will regret it later in life.

Life is hard, and it gets harder! It won’t get easier, you need to get stronger. You will experience your fair share of ups and downs but always remember three things:

Don’t give up when you fall down.

Stay humble when you are on your way up.

Remember that after every dark night there will be a bright morning,

You are not the center of the universe. The sooner you realize this the better, lower your expectations and try to stand up on your feet, work hard and overcome your fears and flaws. One day you will find out that the only people who will stand by you is your family, particularly your parents.

Always be there for your parents.

Make time for your kids

Be loyal to your wife.

You will never get rich working for someone else. If you actually want to grow and have your dream career/job then start your own business, spend all those energy and talent working for yourself instead of working for someone else all your life. You will grow much faster working a day for yourself than a month for somebody else.

If you are spending 8 hours working for someone else, make sure to make some time to work on/for yourself. Take care of yourself mentally and physically.

Exercise

Eat healthy

Read a lot and never stop improving

keep investing in yourself, it will always pay off.

Learn to say “no”. Be kind and nice to people, be honest at your job, but there are times when you seriously need to say “no” to people, learn how and when to do that.

A college degree does not guarantee anything. No need to elaborate on this one.