You use the expression ‘Lose Your Head’ to indicate the tendency to become overly
emotional or confused about something.
Example of use: “Be careful not to lose your head. This situation calls for steady nerves!”
Although no one is certain, it is widely believed that the expression ‘lose your head’ comes from the days when beheading was a common form of punishment. If one didn’t behave appropriately, it was likely that one might lose one’s head.