Have you ever noticed that you can be minding your own business, just thinking of what you are going to have for dinner, when a co-worker, relative or loved one comes up to you and asks "Why are you in such a bad mood?" Your reply is "I'm not in a bad mood" and of course, "No, I can tell you are. What is wrong?" soon follows. By this time you are getting a little peeved, but still deny the bad mood. Of course friends never seem to drop this topic until they do put you in a cranky mood, to which they reply "I don't understand, everytime I see you, you are always upset".
My response now - "I'm in a bad mood because I like the view". It makes no sense, but they stop asking that stupid question.