go off the deep end

US /ɡoʊ ɔf ðə diːp ɛnd/
UK /ɡoʊ ɔf ðə diːp ɛnd/
"go off the deep end" picture
1.

to become very angry or emotional, or to start behaving in a crazy way

:
•
When he heard the news, he really went off the deep end.
•
She tends to go off the deep end when she's stressed.
:
go offgo off withgo to the ends of the earthdeepgo off the railsgo off on a tangentend