0 used to say that it is not worth talking to someone because they will not listen to you:
I don't know why I even try to talk to him - I might as well save my breath.
1 to not say anything:
I don’t know why I bother trying to explain this to you – I might as well save my breath.
NYA ORD
European
May 10, 2021
DAGENS ORD
Shimmer
save your breath