Jesus sends his 72 disciples out to preach the Gospel, and they come back rejoicing at the success of their mission. Those who trust in God and obey his call in their lives, as did the seventy-two, will experience God's power acting in and through their lives, which is exactly what Christ wants.  A Christian's happiness doesn't arise from how great we are or how great our achievements have been. It comes from knowing that we matter to God, that God is our Father, Savior and Friend. It comes, as Jesus tells us, from having our "names written in heaven."