The only way one can repent of sin in the sense that they turn from my evil way and walk straight is if God changes theirheart. So repentance is turning to God, who then purifies your heart, then because of God’s work you are able to walk in His ways progressively growing in holiness. . For He writes His Law on our hearts.
If I had to give up my sinful life by the power of the flesh, I would never have come to Jesus. I turned to Him in simple faith, He changed me, and it was what He did in me that changed my external behavior.
He took away my old lives and gave me a new love. Otherwise, I would never have turned away from the sin that I loved above all else.