The Work Of The Gospel

The Law reveals our condition and our sin.  The Gospel is what saves us and redeems us.  From this point it is often assumed that now we need to move on to the Law to sustain us and help us live.  Take a moment and look to the Small Catechism's view of the Gospel at work in our Christian living...

The Third Article: Sanctification
I believe in the Holy Spirit, the holy Christian church, the communion of saints, the forgiveness of sins, the resurrection of the body, and the life everlasting. Amen.

What does this mean?
I believe that I cannot by my own reason or strength believe in Jesus Christ, my Lord, or come to Him; but the Holy Spirit has called me by the Gospel, enlightened me with His gifts, sanctified and kept me in the true faith. In the same way He calls, gathers, enlightens, and sanctifies the whole Christian church on earth, and keeps it with Jesus Christ in the one true faith. In this Christian church He daily and richly forgives all my sins and the sins of all believers. On the Last Day He will raise me and all the dead, and give eternal life to me and all believers in Christ. This is most certainly true. 

By the Gospel the Holy Spirit begins faith in us and also sustains it.  The Christian life is not Law-Gospel-Law but simply Law-Gospel.  The Holy Spirit by the Gospel not only calls and enlightens us but He also sanctifies and keeps us in the faith!