let your hair down
放松自己，表达真实的个性或情感
口语·放松做自己
英文释义
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.
典故来源
源自古代女性将头发盘起以示正式，放下头发则代表放松和私密场合。