a cool head
cool head
The ability to remain calm and rational during stressful situations. The successful outcome of the hostage situation was due to the police officer's cool head.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
a cool head
COMMON If you have a cool head, you remain calm in difficult situations. I have to keep a cool head and try not to let my anger show. I value her cool head when I'm trying to come to a decision.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012