Last night I dreamed I was hurriedly trying to type something into a cellphone. It had a clever keyboard layout, designed to minimize the number of presses for common letters at the expense of rare ones, so ETAONRISH were just one press each. Fortunately I never had to type Q.
So far, so good. There was just one little problem: it didn't match the keys. They were labeled with the standard layout, where the common letter S takes four presses. The phone worked around this problem by showing the captions on an onscreen keyboard, for the convenience of beginners like me.
Unfortunately the ones it showed belonged to a different clever layout - one that tried to reduce keystrokes by spreading them more uniformly across all twelve keys. (This doesn't make a lot of sense, but I was asleep, okay?) So I was reduced to guessing, while both keyboards helpfully misled me, and the efficient layout was for naught.
Remember those easy, carefree flying dreams? I don't have those anymore. Instead I dream about difficulties controlling my flight. This is what happens when you think about usability problems too much. You start to dream bad user interfaces.