lose one's head (over someone or something)
Fig. to become confused or overly emotional about someone or something. Don't lose your head over John. He isn't worth it. I'm sorry. I got upset and lost my head.
lose one's head
see under keep one's head, def. 1.
lose one's head, to
To become so agitated that one cannot act sensibly. This expression, which at one time meant literal decapitation and was used figuratively from the mid-nineteenth century on, differs from the more recent catchphrase “You’d lose your head if it wasn’t screwed on,” addressed to an extremely absentminded person. Thomas Macaulay’s History of England (1855) stated, “He lost his head, almost fainted away on the floor of the House.”