To deeply regret a past action or missed opportunity, but it is now impossible to rectify the situation; too late for repentance.
他当初没有听取朋友的建议，现在项目失败了才来后悔，真是噬脐何及。
He didn't take his friend's advice at the beginning, and now that the project has failed, it's too late for regrets.
Era:
Ancient
Frequency:
Synonym:
Story:
During the Spring and Autumn Period, King Wen of Chu sought passage through the State of Deng to attack the State of Shen. Deng Qihou, the King of Deng, who was King Wen of Chu's maternal uncle, personally welcomed his nephew.
Deng Qihou's son warned his father to be cautious of King Wen, but Deng Qihou ignored the advice and allowed the Chu army to pass and attack Shen.
After King Wen of Chu conquered Shen, on his return journey, he turned his forces to attack the State of Deng.
Deng Qihou was filled with regret, but by then, it was utterly too late.
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