Make Exercise a Habit
This goes without saying, but needs to be said anyway. Since this is a collection of life lessons, it is imperative to include this one: not only must you excercise, but you must make it a habit.
Your excercise could be to walk, run, swim, do yoga or go to the gym. It can be rigorous, or gentle. That does not matter.
What matters is that you get off your ass, and make a habit out of engaging in physical activity.
It makes you feel better physically, it helps your brain function better mentally, and it makes you feel better emotionally – they say exercise is one of the best cures for depression.
Or, live a mediocre life. They choice is yours.