1. Do not lend money to anyone. You will not get it back. Trust me on this one. Not even boyfriends. CORRECTION: Especially not boyfriends.
2. Start working out. Get in the habit early. If you wait for your metabolism to slow as you creep out of your twenties without working out, it will be so very challenging to get into it.
3. Only date people that you really like and that really like you back. I was able to recover a couple of years ago and realize the value in that one. Trust me. Your life is so much better when you can have fun with the person you are dating. (Conversely, I have realized how dating the wrong person can make you a miserable person in all aspects of your life.)
4. Learn that sometimes friends grow apart and don't beat yourself up about it. As you grow up, you learn more about yourself and the kinds of people around which you'd like to spend your time. Let those who don't make you happy fall off the grid. And those that you do love? Hold onto them fiercely. Don't forget to tell them you love them.
5. Get a hobby. Odds are good that your job will be something to fund your life, not your lifelong passion. That's OK, I think. Just make sure you have an activity that makes you happy, something about which you feel passionate. I think that makes "working for the weekend" A-OK. Plus it makes you a more well-rounded person.
6. You really don't have to wash your hair every day. This is a rather recent discovery I have made. Certainly, I am wondering how many hours of my life I have spent washing my hair when I didn't really need it. Bobby pins and dry shampoo (or baby powder in a pinch) work magic.
So I really wanted to have a list of ten. But at this moment, I am having trouble coming up with more than six important things I have learned in my twenties. I guess these means I am not ready to turn thirty. Oh well. Guess I'll stay twenty-nine.