Self-respect is the root of discipline: The sense of dignity grows
with the ability to say no to oneself.

-- Abraham Joshua Heschel 1907-1972

"Meditate. Live purely. Be quiet. Do your work with mastery. Like the moon, come out from behind the clouds! Shine." 
(Buddha) 

"Becoming is superior to being." 
~ Paul Klee

"Your ability to discipline yourself to set clear goals, and then to work toward them everyday, will do more to guarantee your success than any other single factor."

Brian Tracy in The Power of Discipline

"In order to win, we pay with energy and effort and discipline. If we lose, we pay in disappointment, discontent, and lack of fulfillment."

(Maya Angelou)