When the sexual enjoyment derived from one's own pain/
humiliation clashes with their want to end their own life. It usually forms into wanting someone to hurt them
to the point of fatality, masking it in a sexual light.
Her: "I want you to choke me."
Him: "Okay."
Her, later: "Oh my god, please
step on me."
Him: "Okay...?"
Her, even later: "
Step on me and just crush my spine, dude!"
Him: "I'm mildly
uncomfortable now. You're bordering on suicidal masochism."