Is it a rule that, if you've closely followed five programmes in a six part series, something will prevent you from watching the grand finale?
Is it a rule that you'll get a spot on your nose just when you've got friend you've not seen for ages coming to stay?
Is it a rule that it'll rain the day you've had your hair done?
Is it a rule that really fat* people have to sit next to you on the bus?
Is it a rule that taxi drivers have to stop so that the passenger door is right next to a big puddle?
Is it a rule that someone will call for a chat when you're up to here (*gestures point quite high up) with things to do?
Is it a rule that, just after you've hoovered, you'll drop a big pile of something dusty or granular?
Is it a rule that, when you put black jeans in the wash, there'll be a tissue in the pocket?
No? SO WHY CAN I RELY ON THESE FACTS SO COMPLETELY!?
(NB I'm actually in a fairly prosaic mood. I mean, all of the above rules have proved themselves to exist today, and I've dropped a few things, lost a few things, accidentally hoovered up a few things, but I'm feeling fairly tra-la-la about it all. Just, y'know, avoid giving me any sharp objects of children to hold in the next 24 hours, just in case).
* If not fat, then smelly. If not smelly then squirmy. If not squirmy then downright flaming mental.