"If you pursue it long enough, running can certainly teach you about mindlessness . . . It takes you down deep and shows you the beauty of pursuing a 'single necessity.' Even without intending to, by training the body to accept long distances, you train the mind what not to think about, such as how much long-distance running hurts and how slowly time passes. Surrender--an acceptance of the fate you've chosen--provides you with the ability to endure more suffering, and the more times you do it, the higher the pain threshold rises and the more finely tuned your ability to endure becomes. Owning responsibility for what you're doing, whatever that may be, empowers."
--Marshall Ulrich, Running on Empty.