Only those who try to resist temptation know how strong it is…That is why bad people 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, on the power of sin, from An Arrow Pointing to Heaven, by Rich Mullins, January 1st, 2000
from: http://www.dickstaub.com/