You must stay calm.

你可一定要保持冷静。

youdao

Ok but you must stay calm. Do you want me to give you a lift?

好，不过你可一定要保持冷静。要不要我捎你一程? ?。

youdao

You must stay calm, ask the player to leave the field of play, allow the goal to stand and later report all the facts to the competition and sanctioning authority.

你必须冷静下来，然后将红牌球员罚出场外，但是判罚进球有效。在比赛之后向竞赛和纪律委员会报告发生的一切。

youdao

Often you hear that if stimulants like Ritalin, Vyvanse, or Adderall help people stay calm, that means that they must have ADHD.

FORBES: NYT Hits The Problem With ADHD Drugs: They Work