I doubt that Paul had huge personal problems with sin. Still, he had the wisdom to realize what lived on in his flesh—this “bondage to sin,” as he describes it. He knew that pride—the underlying root of all sin—remained a powerful enemy which could resurface at any moment. Even though he had become that new creature in Christ, Paul makes it very clear that he carried his old man—his flesh—into his new life in the Lord.
It’s a problem for us, isn’t it. Regardless, Paul totally understood the issue: “It’s not really me doing it, “but sin which dwells in me.” Instead of finding fault with who we have now become in Christ, Paul lays the blame for this weakness at sin’s door. Yet it’s not “the devil made me do it” syndrome. It’s simply me: “I am of flesh, sold into bondage to sin.”
From Free from the Power of Sin: the Keys to Growing in God in Spite of Yourself