南城以南思念不归北城以北深海无眠
[nán chéng yĭ nán sī niàn bù guī bĕi chéng yĭ bĕi shēn hăi wú mián]
To the south of the southern city, my longing doesn’t end; to the north of the northern city, I lie awake in the deep sea without sleep. A poetic expression conveying ceaseless longing for someone, especially when unable to meet or reconcile.