Psychos can, they have access to their memories.
Severe amnesiacs or disassociative identity disorders are really a lot more of an assholish relationship than if your partner has a thing for murdering you.
I'd rather be tortured in a dungeon by a psycho than love someone who won't remember me the next day. Which is more dehumanizing, being forgotten, memories made for nothing. All because their thick skull, titanium cranium, can't ****ing think.