旧雨今雨却只剩下回忆幻化成蝶却只剩下伤痛
[jiù yŭ jīn yŭ què zhĭ shèng xià huí yì huàn huà chéng dié què zhĭ shèng xià shāng tòng]
Literally meaning 'Old rain and today's rain, but only memories turn into butterflies which bring nothing but pain.' It describes someone who has many sad yet beautiful memories in their past that have transformed into bitter feelings.