If I have a secret someone must know, I hope that person is you.

如果我有一个秘密必须有人知道，我希望那个人是你。

youdao

Case-dough means that someone has some money secretly and would like to keep it permanently secret, especially he doesn't want his spouse to know it, because he has some purpose.

私房钱指某人偷偷地将钱留起来并希望永远没人知道，尤其不希望他的伴侣知道，因为他是有目的的。

youdao

Now I know your secret. Someone is visiting you!

现在我知道你的秘密了，居然有人来找你！

youdao

When I meet someone I think I might like to know better, my secret is to share something about myself that is both personal and maybe a little embarrassing or self-deprecating (I often tell people that I am divorced.) That tends to spark their curiosity and open them up.

WSJ: Advice for Making New Friends: Share But Don't Overshare