Some superstititons are sensible - like do not walk under a ladder because it is unlucky - well who wants paint or something on their head! Others like do not walk on a crack on a pavement just make it slower to get from A to B. Friday 13th is another - it is no more unlucky than any other day of the year so to put off doing something on that date would be rather silly. I am sure you can think of loads more.