I was 21 years old 10 years ago, here goes....
Dont stop going to the Gym, playing football, circuit training, golf etc just because your not enjoying it as much, eventually you will be a big fat knacker and would do anything to be fit once again.
Do put away 25% of your wages every month, believe it or not you can afford it and it will stand you in good stead for the future.
Dont just amble along thinking that something will definately change or come your way....IT WONT, you need to go out and get what you want yourself.
Do learn to accept help from people before everything goes wrong.
That is all