If you had a chance for a ?do-over in life, what would you do differently?

Make better friends... Friends really do bog you down, hold you back, and then put you into a victimhood mentality. Maybe that's why a large percentage of US university students love the victimhood/identity politics.
Take life into your own hands. Accept you're not special. Do whatever you have to do become self-sufficient in life. NEVER depend on others.