save (one's) breath
To refrain from a futile appeal or effort

[TahlilGaran] Dictionary of Contemporary English ▲

save breath
save (your) breath
to not say anything.
She figured that they might as well save their breath — her mind was made up.

[TahlilGaran] English Idioms Dictionary ▲

save one's breath
to keep silent because talking will not do any good; to remain silent because talking will do no good
"You can save your breath and not bother talking to him. He never listens to anyone."

You may as well save your breath and not talk to her as she will not believe you anyway.

[TahlilGaran] English Idioms Dictionary ▲

save one's breath
v. phr., informal To keep silent because talking will not help; not talk because it will do no good.
Save your breath; the boss will never give you the day off.

[TahlilGaran] English Idioms Dictionary ▲