keep it to yourself：保守祕密

I have one thing you can do for

me. But keep it to yourself.

有件事你能幫我做。但你要保密。

I have something to tell you，

you'll keep it to yourself, won't you?

我有件事對你說，你會保守祕密的，是吧！

You'd better keep it to yourself.

你最好守口如瓶。

It is very important。keep it to

yourself.

這件事很重要，千萬不要對別人說。