The two keys to life: running and reading.
When you're running, and you're out there and you're running, there's a little person that talks to you, and that little person says "Oh, I'm tired, my lung's about to pop off, I'm so hurt, I'm so tired, there's no way I can possibly continue." And you want to quit, right? That person, if you learn how to defeat that person when you're running, you will learn how to not quit when things get hard in your life.