Some CSL on this holiday devoted to Eros

And all the time the grim joke is that this Eros whose voice seems to speak from the eternal realm is not himself necessarily even permanent. He is notoriously the most mortal of our loves. The world rings with complaints of his fickleness. What is baffling is the combination of this fickleness with his protestations of permanency. To be in love is both to intend and to promote lifelong fidelity. Love makes vows unasked; can't be deterred from making them. "I will ever be true," are almost the first words he utters. Not hypocritically but sincerely. No experience will cure him of the delusion. We have all heard of people who are in love again every few years; each time sincerely convinced that "this time it's the real thing," that their wanderings are over, that they have found their true love and will themselves be true till death.

And yet Eros is in a sense right to make this promise. The event of falling in love is of such a nature that we are right to reject as intolerable the idea that it should be transitory. In one high bound it has overleaped the massive wall of our selfhood; it has made appetite itself altruistic, tossed personal happiness aside as a triviality and planted the interests of another in the centre of our being. Spontaneously and without effort we have fulfilled the law (towards one person) by loving our neighbor as ourselves. It is an image, a foretaste, of what we must become to all if Love Himself rules in us without a rival. It is even (well used) a preparation for that. Simply to relapse from it, merely to "fall out of" love again, is--if I may coin the ugly word--a sort of disredemption. Eros is driven to promise what Eros of himself cannot perform.

C.S. Lewis, The Four Loves