I Corinthians 9:25-27

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. Therefore I run thus: not with uncertainty. Thus I fight: not as one who beats the air. But I discipline my body and bring it into subjection, lest, when I have preached to others, I myself should become disqualified.