我有点紧张，我努力使自己镇静自若。

I'm shaking, trying to hold something inside.

论过后，你怎么还能保持如此心平气和，镇静自若?。

How can you stay so cool, calm and collected after such a hot argument?

他可以想象出她现在的样子――镇静自若，胸有成竹。

He could visualize her now-composed and competent.

一场争论过后,你怎么还能保持如此心平气和, 镇静自若?

How can you stay so cool, calm and collected after an argument?

我以为他会发火，但他却不声不响地坐在办公桌旁，像法官一样镇静自若。

I had expected him to be angry, but instead he sat quietly at his desk, as sober as a judge.