save (one's) breath

To spare the effort of saying something, doing something, or making an appeal that will be futile. Save your breath, Tom. There's no way they'll agree to the deal. I was going to complain to the phone company about the extra charges, but I decided to save my breath.

Fig. to refrain from talking, explaining, or arguing. There is no sense in trying to convince her. Save your breath. Tell her to save her breath. He won't listen to her.

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.

If you tell someone to save their breath, you mean that they should not bother saying something, because you will not agree to it or you do not want to hear it. `If you're going to tell me about the extra week you want to spend in New York, you can save your breath,' she said.

To refrain from a futile appeal or effort: Save your breath; you can't dissuade them.

Don’t bother to tell me about it. The image of expending one’s breath to utter what no one wants to hear dates from the sixteenth century. In early English parlance it often was to keep one’s breath (or wind) to cool one’s pottage/porridge/broth (by blowing on it). Jonathan Swift (Polite Conversation, 1738) wrote, “Pray keep your breath to cool your porridge.” Today the food-cooling phrase is obsolete, but the first portion survives as a cliché. See also waste one's breath.