Coming to Christ in faith is the first work of renewal the Holy Spirit does in our hearts.
He produces faith in our hearts to believe in Christ for the remission of sins. Salvation is a work of God through the Holy Spirit. Our renewal starts from the day we believed in Christ and were given the right to become children of God.
Now that we are children of God, what is required of us by God?
God requires from us a life of holiness and separation from sin. It not just a requirement. It is what we were created to be: holy (Eph 1:4, 1 Pet 1:15-17). We are called out of the world not to be friends with the world--lust of the flesh, lust of the eyes and pride of life. This, left on our own is a daunting task because as long as we live on this side of eternity, our struggles with the flesh and with sin will continue:
For the desires of the flesh are against the Spirit, and the desires of the Spirit are against the flesh, for these are opposed to each other, to keep you from doing the things you want to do.(Gal 5:17).
The spirit indeed is willing, but the flesh is weak(Matt 26:41).However, despite the struggle, we are not victims of our flesh. We are not left on our own to suffer under bondage of sin. God works in us to will and do of His good pleasure, while we, with the help of the Holy Spirit also work out our salvation with fear and trembling. We need not be overcome by sin. The Holy Spirit renews and gives us strength to be victorious.
How can we access this strength to be victorious?
By submission to God through prayer and feeding on His word:
I appeal to you therefore, brothers, by the mercies of God, to present your bodies as a living sacrifice, holy and acceptable to God, which is your spiritual worship. Do not be conformed to this world, but be transformed by the renewal of your mind, that by testing you may discern what is the will of God, what is good and acceptable and perfect.(Rom 12:1-4).