While writing in a word processor, you try to use code comments to comment-out a line you have written which you are not quite sure belongs in the document.
It's true - there I was, writing a talk I needed to give, and after writing a line and thinking that I was not sure it belonged, I hit the 'Home' key to get to the beginning of the line, and typed "//" and thought the line would go green, indicating it was commented-out (which is what it does in Visual Studio). I need more sleep!
Have you ever done something similar?