只想与你长相厮守只想与你白头到老
[zhĭ xiăng yŭ nĭ zhăng xiāng sī shŏu zhĭ xiăng yŭ nĭ bái tóu dào lăo]
It expresses an eternal promise of wanting only you as my partner. 'To grow old together' here means living alongside someone permanently till gray hair sets in during aging, conveying loyalty and deep love.