有一种感情叫无缘有一种放弃叫成全
[yŏu yī zhŏng găn qíng jiào wú yuán yŏu yī zhŏng fàng qì jiào chéng quán]
Conveys the sentiment that some people are not destined to be together, yet their separation might be for the best; a kind of unrequited love or letting go out of respect or higher purpose rather than selfishness.