On the Holy Spirit
It is quite right that you should feel that “something terrific” has happened to you (It has) and be “all glowy.” Accept these sensations with thankfulness as birthday cards from God, but remember that they are only greetings, not the real gift. I mean, it is not the sensations that are the real thing. The real thing is the gift of the Holy Spirit which can’t usually be—perhaps not ever—experienced as a sensation or emotion. The sensations are merely the response of your nervous system. Don’t depend on them. Otherwise when they go and you are once more emotionally flat (as you certainly will be quite soon), you might think that the real thing had gone too. But it won’t. It will be there when you can’t feel it. May even be most operative when you can feel it least.
From The Collected Letters of C.S. Lewis, Volume III
Compiled in Words to Live By