誓言很丰满感情很骨感
[shì yán hĕn fēng măn găn qíng hĕn gú găn]
Vows are abundant, but feelings are thin or 'Promises are easy to make but hard to keep'. It points out the contrast between making grand statements and the reality of sustaining emotional relationships, highlighting that it's much easier to make promises than to maintain a meaningful connection over time.