For by grace you have been saved through faith, and that not of yourselves; it is the gift of God, not of works, lest anyone should boast. For we are His workmanship, created in Christ Jesus for good works, which God prepared beforehand that we should walk in them. (Ephesians 2:8-10)
We are neither saved by good works nor kept by good works. But the salvation that is by grace through faith in Ephesians 2:8-9 is a salvation that results in good works in Ephesians 2:10. However, those good works are not our good works but God’s, for we are His workmanship.
When we are saved by grace through faith in Christ, though, we do not become robots, operating automatically or by remote control. No, we become born again, and we now have the life of Christ in us, the power and indwelling of the Holy Spirit in us, God Himself at work in us. This new life we have in Christ is responsive to God because it comes from Him. And God is at work in us not only empowering us to do His good pleasure but also creating in us the desire, the will, to do His good pleasure (Philippians 2:13). So the good works that God does in and through us, and which result from salvation by grace through faith, are not a violation of our human will and desire. They are a manifestation of the salvation we receive when we come to Christ in faith.
This means that the change of behavior we experience as believers is not a result of our own works but of God’s. So we need not worry about how much change would satisfy God. For God will always be satisfied with the work He does in us, and He will do whatever work needs to be done in us. And the good work He has begun in us, He will bring all the way through to completion (Philippians 1:6).
This also means that perseverance is not a result of what we do but, rather, a result of what God does in us. Those who have begun in the new birth continue in the new birth. Those who have begun in eternal life continue in eternal life. And those who have begun by grace through faith continue by grace through faith. Because it is God’s doing, not ours.