And of course the presence of God is not the same as the sense of the presence of God. The latter may be due to imagination; the former may be attended with no “sensible consolation.” The Father was not really absent from the Son when He said “Why hast thou forsaken me?” You see God Himself, as man, submitted to man’s sense of being abandoned. The real parallel on the natural level is one which seems odd for a bachelor to write to a lady, but too illuminating not to be used. The act which engenders a child ought to be, and usually is attended by pleasure. But it is not the pleasure that produces the child. Where there is pleasure there may be sterility: where there is no pleasure the act may be fertile. And in the spiritual marriage of God and the soul it is the same. It is the actual presence, not the sensation of the presence, of the Holy Ghost which begets Christ in us. The sense of the presence is a super-added gift for which we give thanks when it comes, and that’s all about it.
From The Collected Letters of C.S. Lewis, Volume III