What happens if you unwillingly do something that will cause you bad luck?
For example, you spill some salt? Well, if that happens you should throw some more over your left shoulder to counterbalance the bad luck. Do you know why? Because it is said that the devil sits behind us on the left side!!!
A more common and general way to avoid bad luck is touching, or knocking on, wood.
What do we use here in Italy to avoid bad luck? 😉