a cool head

基本解释

Keep a cool head when thing go wrong.
出问题时要保持冷静的头脑。
The device, a prototype of which was unveiled this week, is an emotion-sensing system designed to help investors keep a cool head when buying and selling.
刚于本周公布的这项设备的雏形，是一个情绪感知系统，旨在帮助投资方在买卖时，保持冷静。
One could argue that he thrives off that fire in his belly, but at the same time he is supposed to be the finisher, and often the creator, which calls for a cool head.
有人可能会说这是这种高昂的斗志成就了鲁尼，不过同时他在球场上大多数时候很可能即是最后一脚的完成者，也是机会创造的组织者，不过不论是做哪一个都需要冷静的头脑。

"There is no pressure. I have gone through pressure up to this time, so I need a cool head.

You'll need a cool head if the bidding gets overheated, but the boats have clear title.
FORBES: Boat Bargain
Neil will tell us how to profit by keeping a cool head while the markets panic.
FORBES: Steve Forbes Interviews Neil Hennessy
As the chairman knows well, he must always keep a cool head even as others lose their shirts.
ECONOMIST: And Ben Bernanke keeps his cool