ㄌㄜˋㄐㄧˊㄕㄥshēngㄅㄟbēi

  1. 歡樂至極往往轉生悲愁警世通言··秀才一朝交泰》:丞相只道千年富貴萬代奢華誰知樂極生悲一朝觸犯朝廷闔門未知生死。」樂極悲來」、樂極悲生」、樂極則悲」。興盡悲來否極泰來苦盡甘來

extreme joy turns to sorrow (idiom)​; Don't celebrate too soon, things could still go wrong!