lose it

informal

Definition

› to stop being able to control your emotions and suddenly start to laugh, shout or cry: I was trying so hard to stay calm but in the end I just lost it. → See also fight a losing battle → See also lose your cool → See also lose/save face → See also gain/lose ground → See also lose sight of sth → See also lose sleep over sth

(Definition of lose it from the Cambridge Learner's Dictionary © Cambridge University Press)