The main thing is to remain calm.

最重要的是要保持冷静。

I have schooled myself to remain calm under pressure.

我练就一副在压力之下保持镇静的本领。

The police made an appeal to the public to remain calm.

警方吁请公众保持镇静。

He did his best to remain calm, but there was a distinct edge to his voice.

尽管他竭力保持镇静，话音里仍明显带有怒气。

He was taken aback, but he managed to remain calm.

他心里一惊， 但表面上却仍神色自若。