I already know all this! Now, you're just preaching to the choir.

这些我都知道！现在，在" 白费口舌" 。

Still Matthew said nothing and Marilla had a sense of having wasted words and breath.

马修仍然一言不发，玛丽拉有种白费口舌的感觉。

Save your breath, Gaby. It's not gonna happen.

别白费口舌了 加布 不可能的。

Save your breath. She’s already made up her mind.

【breath】别白费口舌了，她主。

Her good advice was wasted on the children.

【waste】她对孩子们的规劝白费口舌了。

You're just shouting into the wind.

在白费口舌。

Don’t try to reason with Paul – you’re wasting your breath.

【waste】别跟保罗讲道理，在白费口舌。

Sometimes a person fights a battle that has been decided or keeps arguing a question that has been settled. We say this is like " beating a dead horse."

有时，一个人可能一直就经决了的战争而战斗，或者一直争论经解决了的问题。我们说，这简直白费口舌(就好象beating a dead horse)。