执子之手若不能与子偕老得一人心若不能白头到老
[zhí zi zhī shŏu ruò bù néng yŭ zi xié lăo dé yī rén xīn ruò bù néng bái tóu dào lăo]
It means 'holding your hand, if I can't grow old with you; finding true love if I can't live together until old age'. This reflects deep romantic longing mixed with resignation. It shows the speaker cherishing every moment they have with their partner knowing it may not last forever.