C.S. Lewis

"…the prayers offered in a state of dryness are those which please Him best…"

"Our cause is never in more 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"

Screwtape in The Screwtape Letters by C.S. Lewis

(If you're not familiar with the screwtape letters, it is a fictional account of an older, more experienced demon giving advice to a less-experienced one on how to keep a Christian from honoring God.)