save one's breath

save one's breath

Refrain from arguing about a lost cause, as in You can save your breath; I'm not going to change my mind. This term was also put as save your breath to cool your porridge (or broth), that is, by not blowing on the too hot liquid. The idea of not expending one's breath to say something another person doesn't want to hear dates from the early 1700s.
See also: breath, save