明知是梦却总是放不下明知是痛却总是放不下
[míng zhī shì mèng què zŏng shì fàng bù xià míng zhī shì tòng què zŏng shì fàng bù xià]
It expresses an inner conflict where the person knows something (like a relationship) is unrealistic ('a dream') or painful, but cannot let go of it.