After entering the Shivering Isles.

I don't suppose your character stayed sane through the whole time s/he spent there.

Meh, my character Lauren wasn't quite sane anyway, considering she massacred random NPCs

This assumes one's avatar was certifiably sane when he/she first entered the Realm of Madness, which may or may not be the case.

As for my decrepit avatar, he treated the entire episode as an alternate reality, a hallucination in which "normal" Nirn rules and behaviors do not apply. He coped, returning to Tamriel little worse for wear. Even now he does not quite know what to make of his long ago misadventures in the Isles.

-Decrepit-