People often think that breaking a mirror may bring you bad luck for 7 years. Mirror superstitions probably evolved from the time when the first humans saw their reflections in a pool of water, believed that the image in a water was their actual soul and to endanger it would mean risking injury to the other self. An ancient myth was that mirrors have magical powers, including the power to foreseen the future and are thought to be devices of the Gods. Thus breaking a mirror would terminate its powers, the soul would be astray form the body and misfortunes would be brought upon the one whose reflection it last held.
It was the Romans who tagged to the broken mirror a sign of seven years bad luck. The length of the prescribed misfortune came from the ancient Roman belief that it took seven years for life to renew itself. If the persons looking into the mirror were not of good health, their image would break the mirror and the run of bad luck would continue for the period of seven years, at the end of which their life would be renewed, their body would be physically rejuvenated, and the curse would be ended.
In old times, mirrors were not cheap and they were low quality and easily defected. In order to avoid negligence it was told that breaking a mirror bring seven years of bad luck. That was simple scare tactic.
A variety of remedies are available to break the spell of misfortune. The Romans are also responsible for little known measure for avoiding the curse useful for anyone who breaks a mirror. The luckless who accidentally break a mirror, and does not wish seven years of ill-lack, must take all the pieces of the mirror and bury them in the moonlight, or take all pieces and throw them into running water, or pound the broken mirror into tiny pieces so that none of them can reflect anything ever again.
If a person who breaks a mirror is too lazy or too busy, to avoid the curse, it just leave the broken pieces the way it was for seven hours (one for each year of bad luck) and then pick it up immediately after the hours are up.
Some other remedies include lighting seven white candies on the first night after breaking the mirror and blowing them out at midnight in one breath, while another is touching a tombstone with a broken piece of the mirror to avoid the bad luck. Perhaps the easiest counter-remedy is to make the sign of the cross by a five-dollar bill, but what is to be done with the five-dollar bill after that it is not known.