The Fighting Temptations

"A silly idea is current that good people do not know what temptation means. This is an obvious lie. Only those who try to resist temptation know how strong it is.… A man who gives in to temptation after five minutes simply does not know what it would have been like an hour later. That is why bad people, in one sense, know very little about badness. They have lived a sheltered life by always giving in. We never find out the strength of the evil impulse inside us until we try to fight it: and Christ, because He was the only man who never yielded to temptation, is also the only man who knows to the full what temptation means—the only complete realist."
C.S. Lewis - Mere Christianity