Jesus is building up his team and like any group of men starting out on a new job they want to know what is in it for them. "What about us. We have left everything and followed you." You can almost hear the pride in their voices, now they want to know what their reward shall be.
They don't get the answer they expect. They think Jesus is going to set up an earthly kingdom and that they shall be his ministers but Jesus tells them their real reward will not be in this life-this life will bring persecution-but in the life to come.
The Christian life demands that we walk in faith. Sometimes we don't see the good times, sometimes we do. But our faith tells us we are being cared for by a loving God. And in the dull times when we feel alone and a little despair creeps in, if we keep going, that's when real growth in faith takes place. Many times the apostles shall be called on to keep going through their difficulties. Why should we be any different?