Don't cut your nose off to spite your face.

Meaning: Self-destructive revenge harms you more than your enemy.

Origin: A medieval image: around 1190 the churchman Peter of Blois quoted a common saying that whoever cuts off his own nose takes a poor revenge, and an Old French form ran "he who cuts off his nose disfigures his face." English has versions from the 16th century, and the "spite" wording from the 19th. It describes harming yourself in a fit of anger meant to hurt someone else.