But I keep under my body, and bring it into subjection: lest that by any means, when I have preached to others, I myself should be a castaway.

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.
But I discipline my body and keep it under control, lest after preaching to others I myself should be disqualified.
But I discipline my body and bring it into subjection, lest, when I have preached to others, I myself should become disqualified.
I discipline my body like an athlete, training it to do what it should. Otherwise, I fear that after preaching to others I myself might be disqualified.
But I punish my body and enslave it, so that after proclaiming to others I myself should not be disqualified.
Bible verse of the day
Blessed are the undefiled in the way,who walk in the law of the Lord.