Zi'an has long been used to such days without warmth. Even for her parents and her brother, she can marry a man she doesn't love at all. Zian is struggling in the quagmire of a formal marriage without warmth and emotion.
Until that person appeared, giving Zian unprecedented warmth and happiness, and rescued her from the quagmire. Just when Zian was trapped in such warmth and couldn't extricate herself, Zian realized that what she had experienced was just an unattainable dream. Those tenderness and romance never belonged to her, and the short-term happiness was just stolen and had to be returned eventually. Even if she was reluctant to give up, she had to say those words.
"Goodbye, Su Yizhi. Goodbye, love."