再回头已成陌生人
[zài huí tóu yĭ chéng mò shēng rén]
Meaning 'Turning Back One More Time Already Makes Us Strangers'. After all the shared experiences, when turning back to seek reassurance again, one might only realize too late how distances grow wider until once close individuals transform into unfamiliar strangers; conveying a deep sadness related to growing apart from others over time without noticing immediately.