不经意的思念是那么痛不经意的回忆是那么痛
[bù jīng yì de sī niàn shì nèi me tòng bù jīng yì de huí yì shì nèi me tòng]
Expresses that unintentional thoughts and memories about someone can unexpectedly bring deep pain or sadness. A profound sorrow that arises accidentally through reminiscence or daydreaming.