Keep your hair on

淡定

例句：

You should keep your hair on at that time.

那时你应保持镇定。

An elephant in the room:

在房间里的大象 ×

不愿意提及或刻意忽视的棘手问题 √

例句：

But nobody is willing to talk about the elephant in the room.

但是大家都不想谈论这个避讳的话题。

A dog's breakfast:

狗的早餐 ×

一团糟 √

例句：

They made a real dog's breakfast of that job.

他们把工作搞得一团糟。