[That wall] might be breached sometime in the future, but for now the only real conversation between them was the roots that had already grown low and deep, under the wall, where they could not be broken.

The most terrible thing, though, was the fear that the wall could never be breached, that in his heart Alai was glad of the separation, and was ready to be Ender's enemy. For now that they could not be together, they must be infinitely apart, and what had been sure and unshakable was now fragile and insubstantial; from the moment we are not together, Alai is a stranger, for he has a life now that will be no part of mine, and that means that when I see him we will not know each other.

Orson Scott Card