To act contrary to one's own desires or principles; to do something one dislikes or knows is disadvantageous while having other options.
他明知熬夜对身体不好，却总是忍不住玩到很晚，真是恶湿居下。
He knows staying up late is bad for his health, but he always can't help but play until very late, which is truly acting contrary to his own wishes.
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