There are so many things that occur to me, but I'll go with something that is sort of a big deal to me.
I'm going to say that a basic skill that a lot of people never learn is to have self-esteem.
My parents, as much as I loved them, did sort of an Irish cultural thing where they insisted I don't "go around thinking you're better than anybody". The result was
that I interpreted that in sort of a "I'm not as good as other people" way and it cost me years of not trusting myself in front of strangers or in public. I was a bit on the shy side
and didn't like walking into a room if I thought there was somebody there that didn't like me, which I now know was ridiculous. I wish that the message I received from them instead
was "believe that you are as good as anybody", because it took me a while to figure that out on my own. Sadly, some people never learn it. There is nothing wrong with putting
yourself out there. Fear of failure is worse than failing, it's debilitating.
Sometimes it seems to me that everything good that has happened to me came from first believing that I could do something or deserved it even if it required overcoming
initial anxiety. One catalyst, in my case, was a Dale Carnegie course called "How to develop self-confidence and influence people through public speaking". I didn't understand
it at that time, but it helped me make some positive changes at a time when I was struggling. I think it should be taught in every High School.
Now, I wouldn't call myself cocky or arrogant, but I don't worry about a lot. I can't remember the last time I was truly afraid of doing something or felt anxious and life is a lot more fun that way.
Self-esteem is a learnable skill that every young person should have, particularly in this era, but it is never too late in life for somebody to figure it out.