From C. S. Lewis, The Screwtape Letters (so think: the “Enemy” = God in this case)
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 doesn’t like, or in the long, dim labyrinth of reveries that have not even lust or ambition to give them relish, but which, once chance association has started them, the creature is too weak or fuddled to shake off.
You will say that these are very small sins; and doubtless, like all young tempters, you are anxious to be able to report spectacular wickedness. But do remember, the only thing that matters is the extent to which you separate the man from the Enemy. 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 Nothing. Murder is no better than cards if cards can do the trick. Indeed the safest road to Hell is the gradual one – the gentle slope, soft underfoot, without sudden turnings, without milestones, without signposts,
Your affectionate uncle,