Wiktionary
lose one's head
vb. 1 (context figuratively English) To be killed, usually in a gruesome manner. 2 (context idiomatic English) To behave irrationally or to lose one's self-control, especially in a distressing situation. 3 (context idiomatic English) To be in love with someone. 4 (context idiomatic English) To be dismissed from a job.
Usage examples of "lose one's head".
When one engages in such horizontal activities, one had better be damned ready to make a lifetime commitment or be prepared to lose one's head, or other body parts.