expression
cannot contain one's anger; can't calm down
Idiomatic expression literally meaning 'the bug in one's stomach won't settle'; used when someone is so angry they cannot calm down. Often implies a sense of righteous indignation or frustration that persists.
彼の失礼な態度に腹の虫がおさまらない。
I can't contain my anger at his rude attitude.
あの言い訳を聞いたら、腹の虫がおさまらなかった。
When I heard that excuse, I just couldn't calm down.
From the folk belief that a 'bug' (虫) in the stomach controls emotions; when the bug is agitated, one cannot calm down. The exact origin is uncertain, but the expression is a traditional Japanese idiom.