let your hair down
放松，放松一下
释义：
(informal) to relax and enjoy yourself, especially in a lively way 放松;轻松一下
例句：
It is only with friends that most people feel they can let their hair down and be themselves.
The office party is a great chance to let your hair down, get to know your colleagues better and enjoy a drink on your employer's dime – in theory.
