There have been times when I think we do not desire heaven; but more often I find myself wondering whether, in our heart of hearts, we have ever desired anything else. You may have noticed that the books you really love are bound together by a secret thread. You know very well what is the common quality that make you love them, though you cannot put it into words: but most of your friends do not see it at all, and often wonder why, liking this, you should also like that.
He goes on to describe that same elusive thread connecting your love of art, your hobbies, your lifelong friendships.
You never had it [i.e., this thing you deeply desire]. All the things that have ever deeply possessed your soul have been but hints of it—tantalising glimpses, promises never quite fulfilled, echoes that died away just as they caught your ear. But if it should really become manifest—if there ever came an echo that did not die away but swelled into the sound itself—you would know it. Beyond all possibility of doubt you would say ‘Here at last is the thing I was made for.’ We cannot tell each other about it. It is the secret signature of each soul, the incommunicable and unappeasable want, the thing we desired before we met our wives or made our friends or chose our work, and which we shall still desire on our deathbeds, when the mind no longer knows wife or friend or work. While we are, this is. If we lose this, we lose all.[†]
† C.S. Lewis, The Problem of Pain (New York: HarperOne, 1996), 150-151.