If something happens and you can' t do anything about it, there is no point in feeling depressed.
如果出了事而你却无计可施时，沮丧是没有用的。
As the saying goes, "It is no use crying over spilt milk. "
俗话说：“覆水难收。”
What you should do, instead, is cheer up and look for a solution to the problem
相反地，你应做的是要振作起来寻找问题的解决之道。