lose your head
US /luːz jʊər hɛd/
UK /luːz jʊər hɛd/

1.
冷静さを失う, 我を忘れる
to become very angry or excited and not behave in a calm, sensible way
:
•
When the fire alarm went off, everyone started to lose their head.
火災報知器が鳴ったとき、みんな冷静さを失い始めた。
•
It's important to stay calm and not lose your head in a crisis.
危機に際しては、冷静さを保ち、冷静さを失わないことが重要です。