Are you superstitious on days like Friday the 13th? These are the origins of 7 common superstitions, like why we knock on wood.

Do you knock on wood or avoid stepping on cracks to prevent something bad from happening? While the origins of some of these popular superstitions seem pretty silly, many people still do them today. We spoke with a few experts to find out where these beliefs come from and why we engage in this "magical thinking."