it's no use crying over spilled milk idiom saying
牛奶泼了，哭也无益;已成定局的事后悔也无用
said to emphasize that it is not useful feeling sorry about something that has already happened
It's no use crying over spilled milk - he's spent all the money, and there's nothing you can do about it. 事已至此，伤心也没用——他把钱都花光了，对此你也毫无办法。