"The New Testament has lots to say about self-denial, but not about self-denial as an end in itself. We are told to deny ourselves and to take up our crosses in order that we may follow Christ; and nearly every description of what we shall ultimately find if we do so contains an appeal to desire. If there lurks in most modern minds the notion that to desire our own good and earnestly to hope for the enjoyment of it is a bad thing, I submit that this notion has crept in from Kant and the Stoics and is no part of the Christian faith. Indeed, if we consider the unblushing promises of reward and the staggering nature of the rewards promised in the Gospels, it would seem that Our Lord finds our desires not too strong, but too weak. We are half-hearted creatures, fooling about with drink and sex and ambition when infinite joy is offered us, like an ignorant child who wants to go on making mud pies in a slum because he cannot imagine what is meant by the offer of a holiday at the sea. We are far too easily pleased."
[Screwtape's advice on temptation:] "Never forget that when we are dealing with any pleasure in its healthy and normal and satisfying form, we are, in a sense, on the Enemy's ground. I know we have won many a soul through pleasure. All the same, it is His invention, not ours. He made the pleasures: all our research so far has not enabled us to produce one. All we can do is to encourage the humans to take the pleasures which our Enemy has produced, at times, or in ways, or in degrees, which He had forbidden. Hence we always try to work away from the natural condition of any pleasure to that in which it is least natural, least redolent of its Maker, and least pleasurable. An ever increasing craving for an ever diminishing pleasure is the formula."