keep calm; don't do anything rash; stay composed
A polite, somewhat formal set phrase used to encourage someone who is upset or panicking to stay calm and not act impulsively. Often used when consoling or warning someone in distress.
Don't panic like that; keep calm.
Stay composed. It's important to stay calm right now.
A polite set phrase combining the honorific prefix お, 気 (spirit/mind), the object marker を, and the adverbial form of 確か (certain/steady). Literally 'make your mind steady', it is used to urge composure.