Daily Chinese Idiom Guessing Game
To brood over something; to have a persistent feeling of resentment or worry that one cannot forget.
耿耿有心事的样子。不能忘怀，牵萦于心。
《诗经·邶风·柏舟》耿耿不寐，如有隐忧。”
She still broods over the argument they had years ago.