1 Corinthians 9:24-27 (NIV) - The Need for Self-Discipline

24 Do you not know that in a race all the runners run, but only one gets the prize? Run in such a way as to get the prize. 
25 Everyone who competes in the games goes into strict training. They do it to get a crown that will not last, but we do it to get a crown that will last forever.
26 Therefore I do not run like someone running aimlessly; I do not fight like a boxer beating the air. 
27 No, I strike a blow to my body and make it my slave so that after I have preached to others, I myself will not be disqualified for the prize.