"But I keep under my body, and bring it isn't subjection: lest that by any means, when I have preached to others, I myself should be a castaway." - 1 Corinthians 9:27
Paul instructs us to live our preaching. What we instruct others in word, we must exemplify in life. How else could he become a castaway even after preaching to others? Only by failure to exercise the very message he had given to others. The carnal man with its condemnation, although dead by the pledge of God (Romans 6:6; Galatians 2:20), is still alive in the flesh. It is as a wild creature that cannot be restrained, but forces itself upon us; trying to dominate our bodies. Although we have the pledge of the "new man", with righteous motives and desires, we must still contend with the rage of the "old man", that lusts after the flesh.
But how do we "keep under" our body, "and bring it into subjection"?
1. Starve it. He who controls our food controls us. As we cannot grow without bodily nourishment, so too the carnal nature cannot thrive without food. It is fed by entertaining ungodly thoughts and lusts, pursuing and executing selfish desires, harbouring hate for one another, and disregarding the things of God (Ephesians 2:3; Colossians 3:5-9). Withholding these will slowly destroy the carnal man.
2. Feed the spiritual man. As we starve the carnal man, we must feed the spiritual man. At any given time, we are feeding one and starving the other. Feed the spiritual man by nurturing thoughts of good and not evil, thoughts of things truthful, honest, just, pure, lovely, and of good report (Philippians 4:8). We obtain these thoughts by spending time with the Source of these thoughts, in the study of the Word and prayer; one, the food; the other, that which gives life to the food.
3. Fight it. As a starving creature will not lay listless with its hunger pangs, but will become vicious and fight for survival, so too the carnal man will contend for its life. Ephesians 6:10-18 informs us of the equipment we need to engage in this spiritual warfare; not only to battle with the principalities without, but also with the powers within. The carnal man within us is the greatest foe we will face in this life. He is greater than Satan; just as the gun is mightier than the shooter.
Also, do not only fight defensively but offensively. It is good to consciously work to avoid sin; staying clear of entertaining temptation and being critical of our company and friends. But this is not sufficient. We must attack the carnal man by doing the works of Christ: thinking good of others, loving each other, speaking good and not evil. Our activity in spreading the love of God is very much essential to keeping under our own sinful self as it is to avoid sin itself.