The Christians describe the Enemy as one ‘without whom Nothing is strong’. And Nothing is very strong: strong enough to steal away a man’s best years not in sweet sins but in a dreary flickering of the mind over it knows not what and knows not why, in the gratification of curiosities so feeble that the man is only half aware of them, in drumming of fingers and kicking of heels, in whistling tunes that he does not like, or in the long, dim labyrinth of reveries that have not even lust or ambition to give them a relish, but which, once chance association has started them, the creature is too weak and fuddled to shake off.
. . . It does not matter how small the sins are provided that their cumulative effect is to edge the man away from the Light and out into the Nothing.
-C. S. Lewis, The Screwtape Letters