On Joy.

...it is that of an unsatisfied desire which is itself more desirable than any other satisfaction. I call it Joy, which is here a technical term and must be sharply distinguished both from Happiness and from Pleasure. Joy (in my sense) has indeed one characteristic, and one only, in common with them; the fact that anyone who has experienced it will want it again. Apart from that, and considered only in its quality, it might almost equally well be called a particular kind of unhappiness or grief. But then it is a kind we want. I doubt whether anyone who has tasted it would ever, if both were in his power, exchange it for all the pleasures in the world. But then Joy is never in our power and pleasure often is.

-C.S. Lewis, Surprised by Joy