Mother was hardworking and earnest her whole life, never once complaining.
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From Sima Qian's Han-dynasty 《报任少卿书》 (Letter to Ren Shaoqing): 意气勤勤恳恳 - describing earnest feelings. Originally meant 'sincere and heartfelt'; over time the sense shifted to steady, unflashy diligence.
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Very common in formal praise of workers, employees, or public servants - often on retirement plaques or eulogies. Describes quiet, reliable effort rather than brilliance.
