Firstly, I would like to say this: I am not, by nature, a superstitious person.
I walk under ladders. I eat black cats for breakfast. And as a once-amateur thespian, I never had a problem talking about Macbeth directly by name ("Scottish Play"? FFS).
Aside from the eating-cats thing, I consider this perfectly normal behaviour.
However. There are two things I seem behaviourally conditioned to do, despite my best efforts (and besides my rational analysis that all I'm doing is self-perpetuating a psychological load of old cock).
The first is an embarrassing affliction, and one that I do my best to hide.
I cannot see a magpie without saluting it.
Rationally, I know it makes no difference one way or the other who or what I salute. But when it comes to magpies, I can't help myself. I've tried not saluting them, but it doesn't help. There's that prickle-prickle-prickle in the back of my head that always, without fail, sees my hand raise up, practically of its own volition, and touch my forehead. The contortions I go through to make this action seem as natural as possible must be a wonder to behold.
It annoys me that I cannot seem to let this one go. It's mental.
The second one is slightly more bizarre: I cannot put new shoes on a table.
No, really.
I blame my Mother. Come home from Barrett's, get new shoes out of bag, go to put them on the side... "Nooooo! Stop!", exclaims Mum, horrified: "Don't put new shoes on the table, it's bad luck!".
The trouble comes when we attempt to nail down the precise temporal boundary that separates "new" and "not new" (and also what precisely we mean by a table -- the rule as applied in my experience appears to have encompassed pretty-much all elevated surface areas around the house).
So, reasons of hygiene aside, any shoes on pretty-much any surface that isn't the floor rattles those childhood memories and leaves me feeling mildly unsettled.
I think Larkin summed it up quite well.