Being a philosophy major, and an overall practical person, I don't like to be superstitious. Or, rather, I don't like to tell people that I'm superstitious. While I have some unusual ones that have their origins in the over-active imagination of my childhood, I also have some of the more common ones. I have a pair of lucky socks. I generally avoid cracks in the sidewalk. I throw spilled salt over my left shoulder. I knock on wood--quite frequently, actually. And I would never walk under a ladder. I do like black cats, though...
Why would a generally rational and practical person do such ridiculous things? I don't really honestly think it will make a difference if I didn't knock on wood, but the heart of superstition is that "just in case" factor. Just in case I might jinx myself, I knock on wood. And while I don't think my socks are actually lucky, despite having shamrocks and horseshoes all over them, a few lucky things have happened to me while wearing them. However, a few unlucky things have happened to me while wearing them as well. And you'd think that would completely disintegrate my theory about their luckiness, but part of being superstitious is the fact that you ignore the facts. You ignore contrary evidence to your superstition because you'd rather be "safe than sorry" by continuing the behavior than stopping it.
Another element to this is, perhaps, superstitions give us a feeling of control. We can control our fate by throwing the spilled salt over our shoulder. We can prevent bad luck by knocking on wood. This, of course, is rubbish. But we still do it. Because just in case something bad happens, it wasn't our fault.
Obsessive compulsive disorder causes superstitious behavior that you can't get rid of. Light switches, door locks, and other commonplace activities take on a new meaning when you have to use them a certain number of times to avoid bad luck.
I won't go off on a rant here, but much of religion, any religion, contains superstitions up the wazoo. Seriously, people once thought that a woman was a witch if she didn't sink when they threw her in the river. If that's not superstition, I don't know what is.
I can't say I'm arguing for or against superstition. In some cases, it's harmless. In other cases, if taken too seriously, it can be a little dicey. So, once again, the key is moderation. Superstition, if you really can't avoid it, is permissible, I suppose, as long as it's done in moderation. But if you get to the overkill phase of superstition where you can't leave a room without flicking the light switch 39 times, you may want to consider therapy.
Happy Friday! (I hope.)