She rarely gets a chance to let her hair down and enjoy life like others do.

她很少有机会会能彻底放松，像其他人那样享受生活。

Harry could see what was funny this time: Professor McGonagall, with her hair in a tight bun, looked as though she had never let her hair down in any sense.

麦格教授的头发总是挽成紧紧的小圆髻，她似乎从来没有把头发散开过。

University life is not all work and no play – it's about having fun too and today Mary needs some persuading to let her hair down – you know, relax and enjoy herself with some extracurricular activities.

大学生活并不全是学习，一点娱乐都没有——生活中也要有一些乐趣，今天就要劝玛丽散开自己的头发——你懂的，就是参加一些课外活动放松一下，享受生活。