For this troper, having given in to temptation from a 30-year old woman who wanted him, thus cheating on what was his girlfriend then. It is something for this troper as being a non-lethal but just as big a MyGreatestFailure as
Kainan having lost his family at the hands of the Moorwen. Even if the girl he cheated on forgave him and tried to rebound, there was too much guilt for this troper to feel.