let your hair down
放松自己，表達真實的個性或情感
口語·放松做自己
英文釋義
to relax and be yourself; to behave in an uninhibited or carefree manner
例句
After the long meeting, she finally let her hair down and danced at the party.
典故來源
源自古代女性將頭發盤起以示正式，放下頭發則代表放松和私密場合。