In William Nicholson's Shadowlands, which is a fictional account of C. S. Lewis' movement from emotional isolation to the world of love, his wife, whom he marries late in life, is afflicted with with bone cancer. At one point in the film (I haven't read the play yet), when Joy seems to go into remission a little, one of Lewis' colleagues, an Anglican priest, comment that he knew how hard Lewis prayed, and "Now God is answering your prayer."
Lewis: "That's not why I pray, Harry. I pray because I can't help it. I pray because I'm helpless. I pray because the need flows out of me all the time, waking and sleeping. It doesn't change God; it changes me."