a hair in the butter”别理解成“黄油中的一根头发”，而真实含义是具有挑战性的情況，难以解决的窘境。

【例句】
Things were going smoothly enough on our road trip until we found out that every hotel in town was booked for the night. Talk about a hair in the butter!
在我们的公路旅行中，事情进行得足够顺利，直到我们发现镇上的每家酒店都被预订了一晚。真是具有挑战性的情况啊！

Forgetting my textbook at school has proved to be a real hair in the butter for my study plans.
事实证明，在学校忘记带课本对我的学习计划来说是一个难以解决的窘境。