This is one of the cruxes of being a Christian: our reward for faithfulness is often more work and responsibility. There are rules to follow, ideals to achieve, and examples to be set. Being human, we will fall short from time to time, often to the derision of others. Yet we need to keep in mind that God knows this. Jesus handed Peter the keys to Heaven, but yet Peter's faith couldn't keep him above water. Jesus knew that this same man who proclaimed Him as the Messiah would also disavow any knowledge of Him in His darkest hour. Yet He still entrusts such a heavy responsibility of him.
While we hope to understand why God does what He does, we need to remember that we cannot see all that He sees, let alone all that He knows. Today's homily compared God to a parent and us to a child needing surgery. The child does not understand the suffering of the moment, but the parent (who is also agonizing over the pain and discomfort of the child) knows that the surgery must be done to save the child's life. God wants to save all of us. He feels anguish at our sufferings, but promises a greater reward.