How to reply to the disappointment 怎样安慰失望情绪

Don't get upset(over it). 别为这件事心烦意乱。
Don't worry(about it). 别担心。
Don't bother yourself(about it). 别为这件事而烦恼。
Don't be so upset. 别那么心烦意乱的。
Don't be so disappointed. 别那么灰心丧气的。
Don't be so serious. 别那么认真。
Don't think about it any more. 别再想这件事情了。

It's not too late to do it. 做这件事情还不晚。
It's the first nad also the last. 这是第一次，也是最后一次。
It's really hard for you. 真难为你了。
It won't happen again. 这们的事情不会再发生了。
We can do something to compensate¹ for it. 我们可以做此事情来补偿。
You'll do it better next time. 你下次会做得好一些。

Take it easy. 别着急。
Take your time. 慢慢来。
Better luck next time. 祝你下次好运。
Things will be better for you . 事情会慢慢好起来的。
There're some ways to make compensate for it . 还有一些补偿的办法

Cheer up . 振作起来。
Brace² up! 打起精神来。
Let it pass. 让它去吧。过去了就不要再想了。