Why people have superstitions

In ancient times, people used natural and supernatural forces to explain common occurrences easily explained by modern science. I read somewhere that breaking a mirror is considered unlucky because people used to believe that mirrors kept part of your soul in them. There is another one that says walking under a ladder is unlucky, this comes from the belief that triangles are supposed to have some sort of significant, mystical meaning (I don't remember what), and a ladder against a wall creates a triangle shape. People were very in touch with their mystical side back then because technology didn't exist, and people only had their minds to entertain themselves with.