Even the Christian's change in life from being a vile sinner to a redeemed saint has never been an issue of them doing it themselves. The Bible says in Philippians 2:12-13 to work out and not work on your salvation and it is God that works in you and not you yourself. 1 Corinthians 15:10 has the Apostle Paul declaring that his changed life was by the grace of God and not himself. Titus 2:11-14 shows how God's unmerited grace is what leads to a changed life. If a person is saved by grace then they are saved from sin by grace. Even the change in the Christian life is by the grace of God which gives them the desire to do good and please God.
Where is my confidence that I have power against sin and the ability to endure to the end? Certainly not in me but in Christ. Philippians 4:13 says that I can do things in Christ who strengthens me and not I can do all things by me. I have no other trust but in Christ the Solid Rock I stand, all other ground is sinking sand.