这一成语出自三国时期蜀汉丞相诸葛亮（181—234年）的《后出师表》，意思是“小心谨慎，贡献出全部精力”。（摘自《现代汉语词典》）

This idiom comes from  “Later Chu Shi Biao”  ( “The Second Memorial on the Expedition Against the North” ) by Zhuge Liang (181–234), Prime Minister of the Shu state during the Three Kingdoms period. It means “to devote oneself to a cause with utmost diligence and energy”. ( extracted from The Contemporary Chinese Dictionary ) 

东汉（25—220年）末年，诸侯割据。魏、蜀（汉）、吴三国崛起，形成三国鼎立的局势。其中，蜀国由刘备建立，他一心以复兴汉室为己任，而诸葛亮则全心全意辅佐刘备。

At the end of the Eastern Han Dynasty (25—220), warlords carved up the realm, and the three states of Wei, Shu (Han), and Wu rose to form the famous tripartite balance of power. Shu was founded by Liu Bei, who regarded the restoration of the Han Dynasty as his lifelong mission. Zhuge Liang, in turn, dedicated himself wholeheartedly to assisting Liu Bei. 

刘备在去世前将儿子刘禅托付给诸葛亮，恳请他继续辅佐刘禅完成复兴汉室的大业。诸葛亮尽心尽力，一面处理国家大事，一面不断劝诫刘禅，希望他能成为一位贤明的君主。

Before his death, Liu Bei entrusted his young son Liu Shan to Zhuge Liang, urging him to continue supporting his heir in the great undertaking of restoring the Han. Zhuge Liang fulfilled this charge with tireless devotion—managing the affairs of state while constantly admonishing Liu Shan to grow into a wise and capable ruler. 

诸葛亮始终将北伐曹魏作为首要目标，然而多次出兵均未成功。228年冬天，诸葛亮准备再次北伐。临行前，他写下了著名的《后出师表》，呈给蜀汉后主刘禅，主要论述北伐的必要性及当前的形势。文中的那句“臣鞠躬尽瘁，死而后已”成了流传千古的名句，表达了诸葛亮为国家和事业竭尽全力、至死不渝的决心。遗憾的是，公元234年，他在此次北伐途中因病逝世。

Zhuge Liang always regarded the northern expeditions against Wei as his foremost mission, yet repeated campaigns ended in failure. In the winter of 228, as he prepared to march north once again, he composed his famous “Later Chu Shi Biao” and presented it to Liu Shan, the ruler of Shu. In it, he argued for the necessity of the campaign and assessed the current situation. The line “I will spare no effort until my last breath” became a timeless quote, capturing Zhuge Liang’s unwavering resolve to devote himself to his country and cause, even unto death. Sadly, in 234, he died of illness during this very campaign. 

诸葛亮的一生常令人叹惋。他拥有过人的智慧和勇气，对君主忠诚，对事业尽心尽力，为后世所敬仰。

Zhuge Liang’s life continues to evoke both admiration and poignancy. He combined extraordinary wisdom and courage with loyalty to his sovereign and tireless dedication to his mission—qualities that have earned him reverence throughout the ages. 

成语“乐不思蜀”同样源自三国时期蜀国的历史故事。

The idiom Lebu Sishu also comes from a historical story of the Shu state during the Three Kingdoms period. 

刘备之子、蜀汉的第二任君主刘禅，治国无能又贪图享乐。诸葛亮去世后，蜀国失去了能够主持大局的关键人物，国力日渐衰落，最终为魏国所灭。之后，刘禅与身边重臣被迫前往魏国首都洛阳。在那里，他们被软禁，并受到严密的监视。

Liu Shan, son of Liu Bei and the second ruler of Shu, was incompetent in governance and fond of pleasure. After Zhuge Liang’s death, Shu lost its central pillar, its national strength declined, and it was eventually conquered by Wei. Liu Shan and his ministers were taken to Luoyang, the Wei capital, where they lived under house arrest and strict surveillance. 

据史书记载，有一次，魏国权臣司马昭设宴招待刘禅。宴会上，刘禅看着舞蹈表演，津津有味，丝毫没有显出亡国之痛。司马昭问他是否还想念蜀国，刘禅答道：“此间乐，不思蜀。”意思是，我在这里很快乐，一点也不想念蜀国。

According to historical records, during a banquet hosted by the powerful Wei statesman Sima Zhao, Liu Shan enjoyed the dance performance with great delight, showing no sorrow over the loss of his state. When asked whether he still longed for Shu, he replied, “I am happy here and do not think of Shu at all. ”

“乐不思蜀”这个成语，常被用来形容那些沉迷于眼前快乐而忘记本心的人。刘禅也因此成为“无能者”的代表，人们常用“扶不起的阿斗¹”来比喻那些没有能力、不思进取的人。

The idiom “Le Bu Si Shu” has since been used to describe people so absorbed in present enjoyment that they forget their true purpose. As a result, Liu Shan became a symbol of ineptitude, often mocked as “the helpless Adou, ” a phrase still used to refer to those lacking ability and ambition. 

1. 阿斗：刘禅的乳名。

   Adou: the childhood name of Liu Shan.