What superstitions do you believe in?

Out of all superstitions created by all different cultures, which ones do you believe? And when and why did you start believing in them?

I feel weird anytime I sweep near someones feet...

I used to have a lot as a kid, but know i don't even pray before sleep to be honest, so, exist a lot of supertitions but it's just like a addiction, drug, bad habit, i dont see it as useful
i'm starting to pray anyway