This has been known to happen to me in the past, I feel quite tickety boo, but rest of world seems to consider me not so. Perhaps my binge drinking (apparently if you have more than two pints in a session you are now a binge drinker) yesterday has caught up with me (I had three pints). Whatever.
But then having pondered the matter, I've decided that there is only one thing worse. That is when you feel truly awful and everyone tells you how fit you are looking. I'm pretty sure I'd hate that.