自怨自艾

From Mencius:

太甲顛覆湯之典刑，伊尹放之於桐三年；太甲悔過，自怨自艾，於桐處仁遷義，三年以聽伊尹之訓己也，復歸于亳。 [Traditional Chinese poetry, trad.]

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太甲颠覆汤之典刑，伊尹放之于桐三年；太甲悔过，自怨自艾，于桐处仁迁义，三年以听伊尹之训己也，复归于亳。 [Traditional Chinese poetry, simp.]

From: Mencius, c. 4^th century BCE, translated based on James Legge's version

Tàijiǎ diānfù Tāng zhī diǎnxíng, Yī Yǐn fàng zhī yú Tóng sānnián; Tàijiǎ huǐguò, zìyuàn zìyì, yú Tóng chǔ rén qiān yì, sānnián yǐ tīng Yī Yǐn zhī xùn jǐ yě, fù guī yú Bó. [Pinyin]

Tai Jia was then turning upside down the statutes of Tang, when Yi Yin placed him in Tong for three years. There Tai Jia repented of his errors, was contrite, and reformed himself. In Tong be came to dwell in benevolence and walk in righteousness, during those three years, listening to the lessons given to him by Yi Yin. Then Yi Yin again returned with him to Bo.

Originally including rectifying the previous wrongdoing. Now only regretting, literally excluding the latter part.

自怨自艾

1. to be full of remorse and self-reproach