From Nanny McPhee
There is something you should understand about the way I work. When you need me but do not want me, then I must stay. When you want me but no longer need me, then I have to go. It's rather sad, really, but there it is.
[Nanny McPhee turns around to walk out of the room, but stops once she hears Simon
We will never want you!
Then I will never go.