To put one’s faith in Christ necessarily involves a total reorientation of one’s life towards God and righteousness and not simply an adding of Christ to one’s previous way of life. The Law, rather than being a means of obtaining righteousness, had the goal of leading us to the end of ourselves in our pursuit of righteousness and to our single-minded focus on God’s grace in Christ as the means of righteousness.
Paul’s gospel is not really one of justification, but of reconciliation. Humanity, because of its sin, exists in a state of rebellion and enmity with God. Despite our best efforts to improve ourselves we find we cannot. Because our problem is not just sinful behavior but really hatred and mistrust towards God, the solution for our problem is not just legal justification but reconciliation. God demonstrates his love for us despite our rebellion. We respond in loving faith and are empowered by the Holy Spirit to love and trust God, to no longer want to rebel.