let your back hair down的用法和樣例：
例句
用作不及物動詞 (vi.)
- It's wonderful to let your hair down at the weekend after you've been working hard all week.
辛苦工作一周後在周末不拘禮節輕鬆一下真是太好了。 - Although Americans are very informal, if you prefer to be more formal in social situations, you may freely act in your own way.
美國人固然不拘禮節，但是你在社交場合中如果高興守點禮節，盡可照你自己的方式做。
