曾经沧海 Once seen the sea
Explanation
比喻曾经见过很大的世面，不把平常的事物放在眼里。
A metaphor for having seen the world and no longer caring about ordinary things.
Origin Story
年轻的书生李白，怀揣着满腹诗情，离开家乡，四处游历。他漫游山水，见过气势磅礴的长江黄河，领略过雄奇险峻的泰山华山，也曾在热闹繁华的长安城中流连。他结识了众多文人墨客，见识了朝堂的政治风云。一次，李白来到一个偏僻的小镇，看到平静的湖水，不禁想起自己曾经游历过的波涛汹涌的大海。他感慨万千，写下了著名的诗句：“曾经沧海难为水，除却巫山不是云。”从此，“曾经沧海”就成为了人们用来形容经历过大世面的人的成语。
The young scholar Li Bai, filled with poetic inspiration, left his hometown to travel. He wandered through mountains and rivers, witnessing the majestic Yangtze and Yellow Rivers, admiring the magnificent Mount Tai and Mount Hua, and lingering in the bustling city of Chang'an. He made friends with many literati and saw the political turmoil of the court. Once, Li Bai came to a remote town and saw the calm lake water. He was reminded of the turbulent sea he had traveled to before. He felt a lot and wrote the famous verse: "曾经沧海难为水，除却巫山不是云." Since then, "曾经沧海" has been used as an idiom to describe someone who has seen the world.
Usage
形容经历过大世面，见过很多东西，因此对一般事情不以为然。常用于描写人阅历丰富，见多识广。
Used to describe someone who has experienced a lot in the world and therefore doesn't care about ordinary things. Often used to describe someone who is experienced and knowledgeable.
Examples
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他曾经沧海，如今对这些小事早已不屑一顾。
ta cengjing canghǎi, rújīn duì zhèxiē xiǎoshì zǎoyǐ bùxiè yīgù
He has seen it all, and now these small matters are nothing to him.
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阅尽千帆，曾经沧海，如今已波澜不惊。
yuè jìn qiānfān, cengjing canghǎi, rújīn yǐ bōlán bùjīng
Having experienced so much, he is now calm and unruffled by these minor events..