Mirrors were once believed to take a piece of someone's soul
Breaking a mirror is thought to bring seven years of bad luck, which stems all the way from the ancient Greeks and Romans. At that time, people were very suspicious of, if not outright frightened by, mirrors; many believed a mirror took a piece of a person’s soul to reflect it back, and if you were unfortunate enough to break a mirror, your soul would be trapped inside it.
Ancient seers and doctors would use water combined with either a colored plate or a looking glass to determine a person’s health or get a glimpse into their future. If the image was distorted or the plate cracked, the questioning individual was deemed very sick or doomed to die. In addition, the Roman culture believed it would take a person seven years to overcome their sickness, and they also thought people’s health in general changed every seven years, which is where the associated bad luck time frame came into play.