Joy--defined
In his spiritual autobiography, Surprised by Joy, Lewis defines Joy with the following passage:
The central story of my life...is that of an unsatisfied desire which is itself more desirable than any other satisfaction. I call it Joy (which has)... only one characteristic in common with Happiness and Pleasure; the fact that any one 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.
This definition gives the clue to the title of his book, for Lewis's spiritual awakening will be along the lines of being "surprised" by the existence and experience of this kind of "unsatisfied desire."
I think this paragraph is significant also for much of what Lewis writes about elsewhere in terms of "greater pleasure" and "greater love."
As I read it, I have found this description to be true, and yet, I've never thought of joy and pleasure in this way. How much brokenness in ourselves and in the world would be healed if we could remember this simple but profound truth: "...Joy is never in our power and pleasure often is."