Yet also realize that the choices you make as a young adult have long lasting repercussions in your adult life. Keep clear of the lawman, steer away from drug/alcohol addictions, don't allow the company you keep to drag you into poor lifestyle choices/situations, and realize that you are capable of nearly anything you set your focus to accomplish.
Great life advice Walker, I would like to second that bit about friends. Know people that make you better yourself instead.
Be the kind of man that educated men immortalize in stone.