The evil eye, known as “mati” (μάτι) in Greek, is a curse thought to be given by a malicious glare that can cause bad luck or loss. The way to ward off the evil eye is to wear it in order to protect yourself throughout the day.
People can knowingly wish negative thoughts on you, but can also do it unknowingly! For example, if you've just had a gotten engaged, had a baby, or earned a promotion; chances are you've got many more eyes on you which makes you more likely to catch the gaze of someone knowingly (or unknowingly) giving you the evil eye.
It's believed that if your evil eye breaks, it's because it's absorbed as much bad and negative energy it can.
The tradition surrounding the evil eye has been around for over 5000 years and while we can't say for certain it works, we like to believe it does.