Have/keep your wits about you
Definition 1 of 1
Pro Tip 1/3Crisis Situations
Use this phrase when someone stays clear-headed during emergencies or troubling times. 
Despite the blackout, the manager had his wits about him and safely evacuated everyone.
Pro Tip 2/3Pressure Handling
It implies someone can handle pressure well, not losing composure when it matters most. 
You'll need to keep your wits about you when you're negotiating with experienced sellers.
Pro Tip 3/3Mental Sharpness
Implies quick thinking and being able to respond or adapt immediately to situations. 
The quiz show contestant kept her wits about her, answering each question correctly and quickly.