Romans 6:15-23
Paul could understand doctrine at a heavier level, but he realised others were not so able.
Notice that when a person surrenders himself to wickedness the result of that wickedness is more wickedness. Sin breeds sin, which breeds sin, which breeds sin. Sanctification is the goal of our Christian life, and the more we yield ourselves in obedience to righteousness, the more that righteousness brings about holiness.
No one is autonomous. Augustine said that a human being is like a horse, and the horse has one of two riders: either Satan or Christ is riding the horse. Before you were justified, Satan was riding the horse. Now that you are justified, Christ is riding the horse. When you were the servants of sin, you were free from righteousness.
Sanctification is the result of this new, and willing, slavery to God. Holiness. Being increasingly conformed to the image of God in Christ. Putting off the old, being adorned with the new. These concepts, these realities, should be the delight and goal of each believer. Nothing should suppress the longing for personal holiness that the Spirit has implanted in our hearts. The contrast between our new estate and our former shameful life (verse 21) should be a shining example to the church and the world of the free gift of eternal life.