The most unlucky day of the year, except maybe for whoever owned the rights to all those horror movies. I wish I knew where the fascination with the number 13 came from. At least in China, their superstition about the number 4 comes from it sounding very close to the word for death.
I love superstitions. There are some I believe and some I don't, but I never simply dismiss them. They're a fascinating look into the human mind and how we can take one small element ("don't whistle backstage in the theatre; that's the signal to drop the sandbags") and turn it into something different, but still related ("whisting backstage at a theatre is bad luck").
Much like my interest in the supernatural, I'm particularly drawn to superstitions that suggest the involvement of magical creatures. If you've grown up in Ireland, you know that you should never break ground in a fairy ring. If you have to dig, let someone else break ground first, then you're safe. You also never fall asleep inside a fairy ring or you might not be able to leave before dawn, or unless you turn your coat inside out and put it back on.
For those who're scratching your heads, fairy rings, or fairy forts, are circles of mushrooms, flowers, trees or stones which have not been arranged in that shape intentionally. They are believed to be home to fairies who will become angry if you disturb them and will curse you for doing so. Most everyone in Ireland has heard at least one story growing up of someone breaking a fairy ring and having something bad happen to them later. Like all good superstitions, no-one really knows where they first heard it, but it's quite a common story, even if most people don't believe it anymore.
Superstitions aren't just ancient stories passed down through generations. Modern society has all kinds of superstitions that influence our lives. Everyone's heard stories of sports players wearing the same underclothes at each game, for example.
Among gamers like myself, there's a common myth that dice have a will of their own, and can turn on a player they don't like, causing poor rolls. Some people blow on their dice for luck. If a die rolls badly too often, it might be consigned to the dice bag for the rest of the game. Another player might only roll theirs when the game calls for it, for fear of using up all the good rolls.
Myself, I'm quite careful about my dice rolls. Don't want to make the dice gods angry, now do I? ;-)