You know what's a bummer...

When you remember something you learned that is perfect for the moment, but you can't remember exactly what it was, but you don't want to misquote it or word it in a summary format because it might lose effect/people might misunderstand you.

:enough!:

Or when you know a word one language, but the other person speaks another language, and that word just won't come out in the language you want it to.

Isn't is weird how that always happens when you need the information! LOL