Live life fully while you're here. Experience everything. Take care of yourself and your friends. Have fun, be crazy, be weird. Go out and screw up! You're going to anyway, so you might as well enjoy the process. Take the opportunity to learn from your mistakes: find the cause of your problem and eliminate it. Don't try to be perfect; just be an excellent example of being human.
As you get older things conk out. It's a bit like a car. As long as it's something the mechanics can fix you can chug on for a few more thousand miles.