We're often discouraged in evangelism because of the response of the world to the gospel, and because of our own failures.  It feels like we'll never accomplish the mission entrusted to us by Jesus, to make disciples of all nations.  However, in Revelation 7, we see that it will be accomplished; we see that God's plan will be fulfilled.  He will use imperfect vessels like us to gather people from all nations before the throne.  This message can be heard at http://archive.org/details/TheFulfillment