“He who cuts off his nose takes poor revenge for a shame inflicted on him.”
Male ulciscitur dedecus sibi illatum, qui amputat nasum suum.
De Hierosolymitana peregrinatione acceleranda (1189), cited from Mary Beth Rose (ed.) Women in the Middle Ages and Renaissance (Syracuse, NY: Syracuse University Press, 1986) p. 29; translation from John Simpson The Concise Oxford Dictionary of Proverbs (Oxford: Oxford University Press, 1993) p. 55.
A similar proverb, Qui son nez cope deshonore son vis, appears in the late 12th century chanson de geste Garin le Loheren, line 2877.