To have something weigh heavily on one's mind; to brood over something and be unable to forget it.
虽然事情已经过去很久了，但她对当年的误会依然耿耿于心。
Although a long time has passed, she still broods over the misunderstanding from that year.
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To have something weigh heavily on one's mind; to brood over something and be unable to forget it.