Six mistakes mankind keeps making century after century:
Believing that personal gain is made by crushing others;
Worrying about things that cannot be changed or corrected;
Insisting that a thing is impossible because we cannot accomplish it;
Refusing to set aside trivial preferences;
Neglecting development and refinement of the mind;
Attempting to compel others to believe and live as we do.
― Marcus Tullius Cicero

Not much else to say. Much to do though, I think starting with the development and refinement of the mind. First of all by stopping belief in fairy tales.