Practice the "absence" of God?

If we cannot “practise the presence of God,” it is something to practise the absence of God, to become increasingly aware of our unawareness till we feel like men who should stand beside a great cataract and hear no noise, or like a man in a story who looks in a mirror and finds no face there, or a man in a dream who stretches out his hand to visible objects and gets no sensation of touch. To know that one is dreaming is to be no longer perfectly asleep. But for news of the fully waking world you must go to my betters.
C.S. Lewis, The Four Loves (1960; Harcourt Brace: 1991) 140-141.