I don't want this to read as a list of regrets. Really a more positive take is that I'm hoping these 38 life lessons can help others!
1. Don't Waste So Much Time
Speaking of regrets, this is my biggest one. I wish I had spent more time on languages, musical instruments, and generally applying myself than on wasting time with friends, watching TV, etc. Life is short. Use your time wisely. You'll have less time when you start working, and even less for quite a while if you have children!