Don't lose your head. 不要惊慌失措。

Lose one's head

定义：To become uncontrolled or wildly excited（失控或疯狂兴奋）
例：When he thought he saw an animal in the underbrush, he lost his head and began shooting recklessly. （当他认为自己看到了草丛中的动物，他惊慌失措，并开始胡乱射击。）

如下情况，可使用此句：

Don't lose your head if your team is in trouble.
如果你的团队有麻烦了，你也不要惊慌失措。