你不放弃我不离陪你忧愁陪你喜
[nĭ bù fàng qì wŏ bù lí péi nĭ yōu chóu péi nĭ xĭ]
It expresses deep commitment and companionship through thick and thin. The user promises not to leave the person they are addressing as long as that person doesn't give up, whether times are hard or good.