The most import advice I would give myself is to always pay attention to that feeling you get in your belly when all sorts of situations arise. It will tell you when you’re in bad company, it stops you from doing dangerous or unwise things, and it also helps with little things like buying the wrong colour or style or spending too much money. That one voice, call it conscience, instinct, gut feeling, whatever you want, it is there to guide you and if you don’t pay attention, things inevitably goes bad.
Secondly, never give up an opportunity to travel. It is one of the best forms of education. Learning that we are a vast and varied world is humbling and teaches us to be more tolerant.
Lastly, formal education is incredibly important. Not only because of better career choices but because it makes you more interesting, disciplined and better problem solver. These are qualities that will help you forever.