用心良苦 painstaking effort
Explanation
指费尽心思，煞费苦心。形容为别人付出很多的心血和努力。
It means to put a lot of thought and effort into something. It describes the great effort and energy one puts into something for others.
Origin Story
老张是一位经验丰富的木匠，他答应为村里新建的学校制作一套精美的桌椅。他夜以继日地工作，不仅精心挑选上好的木材，还反复琢磨每一个细节，力求完美。他甚至在深夜还在工作室里仔细打磨每一个部件，他的妻子多次劝他休息，但他总是摇摇头说：“孩子们需要好的桌椅，我要用心良苦地做好这件事。”最终，老张完成了这套令人赞叹的桌椅，孩子们都非常喜欢，村里人也纷纷称赞他的手艺和用心。
Old Zhang was an experienced carpenter, and he promised to make a set of beautiful desks and chairs for the newly built village school. He worked day and night, not only carefully selecting the best wood, but also repeatedly pondering every detail in pursuit of perfection. He even spent late nights in his workshop carefully polishing each component. His wife repeatedly urged him to rest, but he always shook his head and said: “The children need good desks and chairs. I must do this carefully.” In the end, Old Zhang completed this amazing set of desks and chairs; the children loved them very much, and the villagers all praised his craftsmanship and dedication.
Usage
用于形容为他人付出了很多心思和努力，也常用来表达一种无奈或遗憾的心情。
Used to describe someone who has put a lot of thought and effort into something for others; it's also often used to express a feeling of helplessness or regret.
Examples
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父母为子女的用心良苦，我们应该体会
fumu wei zinu de yongxinliangku,women yinggai tihui
We should understand our parents' painstaking efforts for their children.
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他为这个项目用心良苦，最终还是失败了
ta wei zhege xiangmu yongxinliangku, zhongjiu haishi shibaile
He painstakingly worked on this project, but it still failed in the end.