keep your wits about you!

Keep your wits about you! (be ready to think quickly in a situation and react to things that you are not expecting to) — Не зевай! Не теряй головы! Держи себя в руках. (контекст.)

Example 1: (Benjamin, who graduated from a famous university in the East, asked Elaine out on a date). Elain's father:
I want to you to keep your wits about you tonight. You never know what tricks Ben picked up back there in the East (The Graduate)

Example 2: Give people the benefit of the doubt regarding their sincerity, but keep your wits about you; they might not be as truthful as they seem.

Example 3: I'm not takin' it lightly, Chloe. But we got a job to do here too, and this is no safer than a mountain under a bomb attack. You keep your wits about you, hear?

Example 4: Travelling in Moscow is potentially dangerous- you really have to keep your wits about you, and be one step ahead of the situation.

also
have your wits about you
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If you can keep your wits about you while all others are losing theirs, and blaming you...