沧海桑田你都在身边我就是你想要的明天
[cāng hăi sāng tián nĭ dōu zài shēn biān wŏ jiù shì nĭ xiăng yào de míng tiān]
This phrase suggests a long-lasting companionship, indicating despite drastic changes, the person you love will stay beside you, and you become each other's best future, full of commitment and expectations for the future together.