The moment I started thinking about superstition, I began to see links to being superstitious and writing mysteries. Are mystery writers particularly superstitious people, I wonder?
I think we are attracted to mysteries both as writers and readers, because the mystery novel attempts to make sense of the universe. A crime is committed that disturbs the fabric of the universe and it is up to the detective to solve this crime and thus restore the universe to wholeness. (This is one of the reasons I don't like the noir novel. Wholeness is never restored even when the crime is solved).
So essentially the mystery novel can do what we can't do in real life. As mystery writers we can restore harmony, see that justice is served and good triumphs. We know this doesn't happen in real life. Maybe that's what we also are trying to do with our superstitions--we try to control our luck, our fate and our universe. If a black cat crosses my path, from right to left, I will do well at that job interview. Or as yesterday's commenter put it, if I wear my special earrings I'll ace the interview. And of course wearing those earrings we do well because we feel invincible.
I just re-watched Harry Potter and the Half Blood Prince, in which they brew a potion of Liquid Luck. Harry pretends to give it to Ron who then plays quiddich brilliantly, thinking he can't lose. So what we all need is a secret vial of that liquid luck, don't we? Just a drop on the tongue for those really important occasions,