As the saying goes — it's no use crying over spilt milk.

常言道：覆水难收，后悔也于事无补。

《牛津词典》

Now it's done, regrets are of no avail.; It's no use crying over spilt milk.

事已如此， 后悔也是枉然。

《新英汉大辞典》

It's no use crying over spilt milk.

牛奶泼出了，哭也没有用。

youdao

We all knew what technology was available in this series, so to be crying over spilt milk now is not right.

BBC: ECB's Giles Clarke says referral system is 'a shambles'

There's no point crying over spilt milk.

BBC: Greek finance minister eyes 2014 recovery for economy