lose your cool
lose (one's) cool
To lose control of one's composure, temper, or nerve in a given situation. He really lost his cool when the waiter dropped his food. I really lost my cool during the interview.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
lose your cool
COMMON If you lose your cool, you suddenly get angry and behave in a bad-tempered or uncontrolled way. At this point, I lost my cool and shouted `for goodness sake, stop!' `Why don't you sit down and have a drink?' — `I don't want a drink,' Anne replied, losing her cool.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012
lose your cool
lose control of your temper or emotions. informalFarlex Partner Idioms Dictionary © Farlex 2017
keep/lose your ˈcool
(informal) stay calm/get angry, excited, etc: He was very insulting. I really don’t know how I managed to keep my cool.Farlex Partner Idioms Dictionary © Farlex 2017