behave yourself 好自为之

“好自为之”，意思是自己妥善处置，自己看着办，大多数时候用于劝诫、警告他人。可以翻译为“look out for oneself”，“behave yourself”。也可以用“It's your funeral”表示，指“you think someone is wrong by insisting on doing something in a particular way, but that they will be affected by the bad consequences resulting from it, and you will not”。

例句：

从现在起，请你好自为之。

From now on, please behave yourself.

我帮不了你什么忙，你好自为之吧。

I can’t help you much. Look out for yourself.

随便你吧，你会后悔的，好自为之。

Have it your own way. You'll be sorry. It's your funeral.