Superstitions take over behaviour because our brains try and repeat whatever actions precede success, even if we cannot see how they have had their influence. Faced with the choice of figuring out how the world works and calculating the best outcome (which is the sensible rational thing to do), or repeating whatever you did last time before something good happened, we are far more likely to choose the latter. ... This explains why having personal rituals is a normal part of being human. It is part of our inheritance as intelligent animals, a strategy that works in the long-term, even though it clearly does not make sense for every individual act.
Stafford Via The Dish.