As far as you (and I) are concerned I have no doubt that the fear you mention is simply a temptation of the devil, an effort to keep us away from God by despair. It is often the devil working through some defect in our health, and in extreme cases it needs a medical as well as a spiritual cure. So don’t listen to these fears and doubts any more than you would to any obviously impure or uncharitable thoughts. . . . Of course, like other evil temptations, they will not be silenced at once. You will think you have got rid of them and then they will come back again—and again. But, with all our temptations of all sorts, we must just endure this. Keep on, do your duty, say your prayers, make your communions, and take no notice of the tempter. He goes away in the end. Remember I John iii, 20 “If ( = though) our heart condemn us, God is greater than our heart.”
The Collected Letters of C. S. Lewis, Volume III: Narnia, Cambridge, and Joy 1950-1963. Copyright © 2007 by C. S. Lewis Pte. Ltd. All rights reserved. Used with permission of HarperCollins Publishers. Words to Live By: A Guide for the Merely Christian. Copyright © 2007 by C. S. Lewis Pte. Ltd. All rights reserved. Used with permission of HarperCollins Publishers.