I don't suffer from too many commonplace superstitions. I'm not afraid of the number thirteen; I don't think you have to be born in October to wear opals safely. A rabbit's foot to me only means the rabbit it belonged to had some bad luck. Black cats are welcome to cross my path any time.
It's the same with work. I do certain things that I think are more comfort rituals than actual superstitions, such as wearing an old green shirt on the day I'm going to finish writing a novel, or putting on socks or slippers when I'm working (weirdly, I've never been able to write when I'm barefoot.)
But I do avoid writing certain things in novels for various reasons. Dentists never make it into my stories; I've had too many bad experiences under their care and would no doubt do them great harm on the page. Neither do shrinks, teachers or chiropractors appear in my books for the same reason. They'd all be instant red shirts.
Characters named Sabra, Chastity, Noah and Madison never appear in my stories; I don't like those names. Scenes with animals relieving themselves seem utterly tacky to me (although I have no problem showing humans while they're in the powder room -- go figure that one out.) The most pretentious thing I ever saw another author do was write themselves into a novel as a character, using their real life identity and occupation for the character. I don't even like to write about characters who work as writers, and yet I'm fine with poets in a story.
I don't think there's any sense or logic to it. We like what we like. We avoid what we don't. Sometimes it's good to make ourselves write about something we always avoid (one of the reasons I wrote Roomies, to see if I could make writers funny versus boring.)
So what do you generally avoid putting in a story? Have you ever tried making yourself write something you'd rather not? Let us know in comments.