If you read further in Romans 7:25, Paul thanks Godbfor Jesus Christ who had made it possible for him to defeat sin. And then in chapter 8, he speaks of the Holy Spirit who has enables him to overcome sin. This is what sanctification achieves: empowering us to overcome sin! Yes, it is possible to overcome sin! When we sin, because we are born again and thus have the life of Christ in us, we cannot willfully sin (1 John 3:9). And where we accidentally fall into sin, we immediately are made aware and we repent!