go off the deep end
US /ɡoʊ ɔf ðə diːp ɛnd/
UK /ɡoʊ ɔf ðə diːp ɛnd/

1.
大发雷霆, 情绪失控, 发疯
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.
当他听到这个消息时,他真的大发雷霆。
•
She tends to go off the deep end when she's stressed.
她压力大的时候容易情绪失控。