1 Corinthians 9:25-27

9:25 Each competitor must exercise self-control in everything. They do it to receive a perishable crown, but we an imperishable one.

9:26 So I do not run uncertainly or box like one who hits only air. 9:27 Instead I subdue my body and make it my slave, so that after preaching to others I myself will not be disqualified.