When someone asks you what you're thinking about and you can't remember, so you have to say 'nothing' even though it clearly bugs them that you won't tell them.
I told my girlfriend I was thinking about nothing. She asked what kind of nothing—like peaceful nothing, or *something* nothing? Turns out there's a whole taxonomy of silence I'm failing at. Now when she asks, I just say "probabilities," which makes her madder but at least sounds intentional.