1 Corinthians 9:24-27 (ESV)
Do you not know that in a race all the runners run, but only one receives the prize? So run that you may obtain it. 25 Every athlete exercises self-control in all things. They do it to receive a perishable wreath, but we an imperishable. 26 So I do not run aimlessly; I do not box as one beating the air. 27 But I discipline my body and keep it under control, lest after preaching to others I myself should be disqualified.