Do you not know that those who run in a race all run, but one receives the prize? Run in such a way that you may obtain it. 25 And everyone who competes for the prize is temperate in all things. Now they do it to obtain a perishable crown, but we for an imperishable crown. 26 Therefore I run thus: not with uncertainty. Thus I fight: not as one who beats the air. 27 But I discipline my body and bring it into subjection, lest, when I have preached to others, I myself should become disqualified.
— 1 Corinthians 9:24-27.
As a runner in a race, or a boxer in a fight, Paul strives to conquer for Christ. To do this he exercises self-discipline so that his own faith is not shipwrecked and that his example will be clear and consistent to those to whom he has preached. [The Bible Panorama.]