The first [thing] is itself the memory of a memory. As I stood beside a flowering currant bush on a summer day there suddenly arose in me without warning, and as if from a depth not of years but of centuries, the memory of that earlier morning at the Old house when my brother had brought his toy garden into the nursery. It is difficult to find words strong enough for the sensation which came over me….It had taken only a moment of time; and in a certain sense everything else that had ever happened to me was insignificant in comparison.
The second glimpse came through Squirrel Nutkin….it administered the shock, it was a trouble. It troubled me with what I can only describe as the Idea of Autumn….the experience was one of intense desire….
[T]he third glimpse came through poetry….
The reader who finds these three episodes of no interest need read this book no further, for in a sense the central story of my life is about nothing else….the quality common to the three experiences; it is that of an unsatisfied desire which is itself more desirable than any other satisfaction. I call it Joy….Joy is never in our power and pleasure often is.
C.S. Lewis, Surprised by Joy, pp. 16-18 (emphases mine)