"No, no no," she said. "You don't understand. Not that kind of longing. It was when I was happiest that I longed most. It was on happy days when we were up there on the hills, the three of us, with the wind and the sunshine...where you couldn't see Glome or the palace. Do you remember? The colour and the smell, and looking across at the Grey Mountain in the distance? And because it was so beautiful, it set me longing, always longing. Somewhere else there must be more of it. Everything seemed to be saying, Psyche come! But I couldn't (not yet) come and I didn't know where I was to come to. It almost hurt me. I felt like a bird in a cage when the other birds of its kind are flying home."
She kissed both my hands, flung them free, and stood up. She had her father's trick of walking to and fro when she talked of something that moved her. And from now till the end I felt (and this horribly) that I was losing her already, that the sacrifice tomorrow would only finish something that had already begun. She was (how long had she been, and I not to know?) out of my reach, in some place of her own.
Since I write this book against the gods, it is just that I should put into it whatever can be said against myself. So let me set this down: as she spoke I felt, amid all my love, a bitterness. Though the things she was saying gave her (that was plain enough) courage and comfort, I grudged her that courage and comfort. It was as if someone or something else had come in between us.
~C.S. Lewis, Till We Have Faces, Chapter 7, (1956)