When you share a bond of emotional contingency with someone, it sometimes happens that features of their style of living are so incompatible with yours as to destroy more of your own personal utility than the bond can generate. It's a nasty situation, which we often adapt to by laboriously self-modifying the bond away. Colloquially, this is called "getting over someone".

It's quite a reasonable response -- but it's also a voluntary one. I'm considerably less thrilled by Lewis including it as part of the salvation package by default. That seems -- well, manipulative is one word for it, but convenient might be an even better one. It's as if he's resolved a conflict between human emotion and his religious beliefs by declaring that the conflict magically won't exist in any sense that matters long-term.

Of course, that's not much comfort to the living people whose loved ones he's implicitly condemned to Hell.