Screwtape offers a helpful image:
Think of your man as a series of concentric circles, his will being the innermost, his intellect coming next, and finally his fantasy. You can hardly hope, at once, to exclude from all the circles everything that smells of the Enemy: but you must keep on shoving all the virtues outward till they are finally located in the circle of fantasy, and all the desirable qualities inward into the Will. It is only in so far as they reach the Will and are there embodied in habits that the virtues are really fatal to us. (I don’t, of course, mean what the patient mistakes for his Will, the conscious fume and fret of resolutions and clenched teeth, but the real centre, what the Enemy calls the Heart.) All sorts of virtues painted in the fantasy or approved by the intellect or even, in some measure, loved and admired, will not keep a man from Our Father’s house: indeed they may make him more amusing when he gets there.
The Screwtape Letters. Copyright © 1942, C. S. Lewis Pte. Ltd. Copyright restored © 1996 C. S. Lewis Pte. Ltd. All rights reserved. Used with permission of HarperCollins Publishers. A Year With C.S. Lewis: Daily Readings from His Classic Works. Copyright © 2003 by C. S. Lewis Pte. Ltd. All rights reserved. Used with permission of HarperCollins Publishers.