We cannot pray…unless we believe that, no matter how barren our experience has become, our Father is still there for us. In The Screwtape Letters, C.S. Lewis has the senior devil explaining to the junior devil that this tenacious faith in God is the tempter’s greatest defeat in our souls.
Sooner or later [God] withdraws, if not in fact, at least from their conscious experience, all those supports and incentives….It is during such trough periods, much more than during the peak periods, that [the Christian] is growing into the sort of creature He wants it to be. Hence the prayers offered in the state of dryness are those which please Him best…
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.
(quoted in When God Comes To Church: A Biblical Model For Revival Today, by Raymond C. Ortlund, Jr.; emphasis and paragraphing mine)