不遗余力 Spare no effort
Explanation
不遗余力指不保留任何力量，竭尽全力。形容做事非常努力，全力以赴。
Bù yí yú lì means not reserving any strength, doing everything one can. It describes someone who works very hard and goes all out.
Origin Story
话说战国时期，秦国攻打赵国，势如破竹，秦王嬴政下令不遗余力地进攻，企图一举歼灭赵军。秦军兵锋锐利，赵国屡战屡败，岌岌可危。赵王紧急召集大臣商议对策，群臣忧心忡忡，束手无策。这时，一位年轻的谋臣站出来，他分析了秦国的战略，认为秦国这次攻势猛烈，但长久以往，后勤补给必然出现问题。他建议赵王坚守城池，同时积极寻找其他国家结盟，拖垮秦国的战争意志。赵王采纳了他的建议，秦军在赵国腹地久攻不下，粮草匮乏，士气低落。最终，秦军不得不撤军，赵国避免了灭顶之灾。这件历史事件，就很好地诠释了不遗余力这一成语的含义，它强调的不仅仅是努力，更重要的是策略和坚持。
During the Warring States period in China, the Qin state attacked the Zhao state. King Zheng of Qin ordered an all-out attack, hoping to annihilate the Zhao army in one fell swoop. However, the Zhao state fought back bravely. A young advisor advised King Zhao to defend the city and seek allies to weaken the Qin army's resolve. King Zhao followed the advice, and the Qin army ultimately retreated after their resources had been depleted. This historical event demonstrates that success depends not only on effort but also on strategy and perseverance.
Usage
形容做事非常卖力，不遗余力地工作。
To describe someone who works very hard and devotes themselves entirely to a task.
Examples
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为了这次演出，她不遗余力地排练，最终取得了成功。
wei le zhe ci yan chu ta bu yi yu li de pai lian zhong yu qu de le cheng gong
She rehearsed tirelessly for this performance and finally succeeded.
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面对困难，我们应该不遗余力地克服。
mian dui kun nan wo men ying gai bu yi yu li de ke fu
In the face of difficulties, we should spare no effort to overcome them.