Some have already been mentioned, but as a married 38-year old with kids, these are my 5 cents. Good luck & HBD.
1. Keep skating, no matter how good/bad you are. You'll make friendships that will be deeper and last much longer than with any other sport.
2. Get a degree. No matter what you decide to do later in life, a degree is the only thing that cannot be taken from you.
3. Skip long-term dating. Spend your time on what you really want to do - either dating more women, skating or learning something else. Don't worry about love, you're too young for that.
4. Enjoy the physical strength of an adult but the flexibility of a youngster.
5. Save money. Don't need to be much, but save anything you can as you will need it later. . Once it's GO for a life situation change, you don't have that restraint and can just go for it.
6. Be social and travel. The more you see of the world and the more people the better - you'll learn more about yourself and about others more than ever before/after. This brings a maturity that will help you navigate further in life and career-wise .
7. Enjoy life. You'll only be in your 20's once.
People that say "30 is the new 20" are wrong and trying to find excuses for pissing away their 20's - whatever your priorities are, do them now and don't wait.