在你婚礼上唱分手快乐
[zài nĭ hūn lĭ shàng chàng fēn shŏu kuài lè]
This nickname expresses a heart-wrenched emotion, where someone is forced to let go of their loved one and wish them all the happiness at their wedding, though deep inside they feel extremely sad and are saying 'farewell'. This phrase conveys the bittersweet experience.