An apple a day keeps the doctor away. if you step on a crack, you'll break your mother's back. Don't sweep your house on New Year's Day or you Woll sweep good fortune away if you wash your hair on the day of a test, the Water will clean your memory and your will forget everything you studied. if your break a mirror, seven years of bad luck is unavoidable. these are examples of some the many superstitions around the world.