When a man turns to Christ and seems to be getting on pretty well, he often feels that it would now be natural if things went fairly smoothly. When troubles come along--illnesses, money troubles, new kinds of temptation--he is disappointed. These things, he feels, might have been necessary to rouse him and make him repent in his bad old days; but why now? Because God is forcing him on, or up, to a higher level: putting him into situations where he will have to be very much braver, or more patient, or more loving, than he ever dreamed of being before.

The command "Be ye perfect" is not idealistic gas. Nor is it a command to do the impossible. He is going to make us into creatures that can obey that command. He said (in the Bible) that we were "gods" and He is going to make good His words. If we let Him--for we can prevent Him, if we choose--He will make the feeblest and filthiest of us into a god or goddess, dazzling, radiant, immortal creature [...] Nothing less. He meant what He said.

Mere Christianity -- C. S. Lewis