expression, godan verb (-u)
lose one's mind; go crazy; lose one's senses
Used when someone becomes mentally unstable, irrational, or acts wildly. Often implies a temporary loss of reason due to shock, anger, or intoxication.
あまりのショックで彼は正気を失った。
He lost his mind from the shock.
酒
I lose my senses when I get drunk.
expression, godan verb (-u)
Refers to physically losing consciousness, fainting, or passing out. Less common than the mental sense; 意識を失う is more frequent for this meaning.
彼は頭を強く打って正気を失った。
He hit his head hard and lost consciousness.