眷恋日日夜夜未停歇滋味酸酸楚楚两人怨
[juàn liàn rì rì yè yè wèi tíng xiē zī wèi suān suān chŭ chŭ liăng rén yuàn]
This depicts an unceasing attachment day and night, full of bitter and sorrowful feelings, with two hearts harboring grievances for each other. It's about deep longing accompanied by pain.