Changing the way people act is the fruit of repentance. Repentance is not behavioral change; it results in behavioral change. Repentance happens in your mind. That 's why John the Baptist says to produce fruit in keeping with repentance. "I preach that they should repent and turn to God and prove their repentance by their deeds" (Acts 26:20).As Warren points out, our actions are changed by our hearts, our hearts are changed by our minds, and our minds are changed by the Word of God.
Update: As one commenter notes, it was Paul and not John quoted in Acts 26:20.