C.S. Lewis wrote a famous book titled The Screwtape Letters. The plot line is that of a senior demon instructing his nephew (Wormwood) on how to tempt and undermine the faith of the Christian man to whom he has been assigned. If you have not read the book, I recommend it. Here are a few great excerpts.
“It is funny how mortals always picture us as putting things into their minds: in reality our best work is done by keeping things out.”
“Gratitude looks to the Past and love to the Present; fear, avarice, lust, and ambition look ahead.”
“Do not be deceived, Wormwood. Our cause is never more in danger than when a human, no longer desiring, but still intending, to do our Enemy’s will, looks round upon a universe from which every trace of Him seems to have vanished, and asks why he has been forsaken, and still obeys.”
“When He [God] talks of their losing their selves, He means only abandoning the clamour of self-will; once they have done that, He really gives them back all their personality, and boasts (I am afraid, sincerely) that when they are wholly His they will be more themselves than ever.”
“The Future is, of all things, the thing least like eternity. It is the most temporal part of time–for the Past is frozen and no longer flows, and the Present is all lit up with eternal rays.”
“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. Murder is no better than cards if cards can do the trick. Indeed the safest road to **** is the gradual one–the gentle slope, soft underfoot, without sudden turnings, without milestones, without signposts.”
“The Enemy wants to bring the man to a state of mind in which he could design the best cathedral in the world, and know it to be the best, and rejoice in the fact, without being any more (or less) or otherwise glad at having done it than he would be if it had been done by another. The Enemy wants him, in the end, to be so free from any bias in his own favour that he can rejoice in his own talents as frankly and gratefully as in his neighbour’s talents–or in a sunrise, an elephant, or a waterfall.”
“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 (God’s) ground…He [God] made the pleasure: 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 [God] has produced, at at times, or in ways, or in degrees, which He [God] has forbidden. ”