I wouldn't tell myself anything because I wouldn't listen! It's a well known fact that Teenagers know everything, 21 year olds know nearly everything and Middle aged and old people know virtually nothing!
Take up yoga. The benefits of yoga are unticipated for both body and mind.
Learn to sing. Nothing has given me more satisfaction and relaxation than being able to sing.
Don't overstress your body, it wears out the cartilage. Having bad kness is a pain.
Avoid loud noise it can permanently damage your hearing. I have spent the past two years with tinitus from singing very loudly with amplified instruments.