Okay, here's mine.

Some decades ago I was making a chicken dish, just for myself. This dish had a lot of paprika in it -- I mean a lot. (I don't remember the details, but I know it wasn't paprikash.) Anyway, I got the cayenne pepper mixed up with the paprika, and ended up with the hottest chicken I have ever run across.

When we talk about something being "unbelievable", we usually don't mean that literally. We believe it. But my chicken really was unbelievably hot, as in, I didn't believe the pain in my mouth could possibly come from my chicken. I figured I must be having some other problem, unrelated to food. So I ate it all, by which time I was dying.

Then I noticed the cayenne, still sitting innocently on the counter, and I felt like a complete moron.