你都不回头怎知我在你身后
[nĭ dōu bù huí tóu zĕn zhī wŏ zài nĭ shēn hòu]
Translates to 'If you don't look back, how would you know that I am behind you?' It metaphorically conveys a situation where one party is oblivious to the other’s presence or affection due to neglect.