As I near the end of my twenties, I've been fortunate to have amazing people in life who's taught me great lessons. Lessons I'm still learning, but some of which are below...

1. Your 20's are like investments with compound interest. Small, smart deposits equal huge rewards. And diversify.
2. The things that you fear most, that are most uncomfortable, are often most important for you to do. And you might as well do them if it's related to that "big dream", because time will pass anyway. And in your twenties often the worst thing that can happen is you move back in with your parents (Thank you Molly Mahar;)). So do it now while you have relatively little to lose, and more time to rebuild than you ever will again.
3. Get a mentor. And another. And another...
4. Read more, never stop trying to learn, cling to your idealism and don't give up on your dreams. Surround yourself with those who push you, believe in you, will give you the advice you need to hear but don't want to (and know when to give you the advice you ask to hear when needed because sometimes you just need to shelter/protect your confidence).
5. Choose a real partner in life. Your strategic alliance (ref. Napoleon Hill).
6. Have an opinion.
7. Listen. And be open to other's opinions.
8. Set goals and write them down. Celebrate your successes then write new ones.
9. Relationships are like bank accounts. You have to make deposits in order to make a withdrawal. And if you overdraw, there will be fines.
10. Invest in a tailored suit, a fabulous set of shoes and yourself.

But mostly, I've been fortunate to learn not to take health for granted. To cherish your loved ones - friends and family. Learn when to walk away (when something is no longer healthy for you) and when to forgive. Life isn't linear. You often live in circles and won't be able to make sense of things looking forward. But when you look back it's laid out as clear as a map. So don't worry about making the wrong decision. Just make a decision and own it. You're can never wrong if you learn something. And last but not least, have fun and make time to live.