偏執狂 的英文怎麼說?

A: I got fired by the school again for throwing tantrum at the students.
B: Why did you want to be a teacher? You certainly don't have the qualities to be a teacher.
A: It's an obsession. I've always wanted to teach ever since I was a kid.
B: I understand, but you need to go see a shrink about your obsession.