keep (one's) wits about (someone)

Translations
быть начеку
You need to keep your wits about you when walking through the city at night.
Тебе нужно быть начеку, когда идешь по городу ночью.
Definitions
To remain alert, attentive, and able to think clearly in a difficult or dangerous situation.
Words
wit

noun
остроумие
wits

noun
ум
keep

verb
держать