毕竟你爱的是她不是我
[bì jìng nĭ ài de shì tā bù shì wŏ]
Expresses heartache because of unrequited love. 'After all, the one you love is her, not me.' It reveals the sorrow felt by a third party who cannot be with their love interest because their love is directed toward someone else, showcasing unfulfilled longing and acceptance of reality.