This discovery flashed a new light back on my whole life. I saw that all my waitings and watchings for Joy, all my vain hopes to find some mental content on which I could, so to speak, lay my finger and say "This is it," had been a futile attempt to contemplate the enjoyed. All that such watching and waiting ever could find would be either an image (Asgard, the Western Garden, or what not) or a quiver in the diaphragm. I should never have to bother again about these images or sensations. I knew now that they were merely the mental track left by the passage of Joy — not the wave but the wave's imprint on the sand. The inherent dialectic of desire itself had in a way already shown me this; for all images and sensations, if idolatrously mistaken for Joy itself, soon honestly confessed themselves inadequate. All said, in the last resort, "It is not I. I am only a reminder. Look! Look! What do I remind you of?"
From C.S. Lewis - Surprised by Joy : The Shape of My Early Life (1955) ~ Chapter XIV