First of all, it comes from Anne Baby's novel: The Golden Age of Su Nian. "White tea has nothing to do with happiness, and gentleness is only for the right person."
Second, from the Han Dynasty Sima Xiangru's wife Zhuo Wenjun's "White-headed Songs". "I want to win a heart, and I don't want to leave each other." "One heart" refers to a person's sincerity, a sincere person.
Interestingly, the subject of "tenderness is for you, and understanding [jiě yì] is inseparable" can refer specifically to oneself, so as to understand that understanding, tenderness and gentleness are all gifts given by God, and they cannot be separated, showing a little narcissism!
(2) It can also be yourself and so-and-so. I gave you all my "gentleness". You can't leave me, understand?