Which superstition do you most believe in?

Friday the 13th is considered an unlucky day in Western superstition. Superstition is the belief in supernatural causality — that one event causes another without any natural process linking the two events — such as astrology, religion, omens, witchcraft, prophecies, etc., that contradicts natural science.
To celebrate the upcoming Friday the 13th, which of these common superstitions are you most likely to believe?

Discuss the list here