Xue Mimi and Wang Licheng were classmates for 12 years. After the college entrance examination, Xue finally got together with Wang after many setbacks. The biggest contributor to all this, besides Xue's best friend Yang Ni, was Xue's diary - "Mr. Little Life".
After Xue's confession was successful, "Mr. Xiaoli" kept reminding Xue the direction of the development of things, and their separation and reunion confirmed the ending told by "Mr. Xiaoli".
On the other hand, Xue and Liu Lunong were entangled in ambiguity and alienated in conflicts because of a series of things, whether in the summer after the college entrance examination or in their lives after college.
The appearance of Chen Jiao, Li Aijia and Ren Tao disrupted the relationship between the three of them and made Xue's choice clear.
But later, Xue became too superstitious about the 'ending' predicted and told by 'Mr. Little Life'. She admitted that she was unsure about the future. She needs to know the ending because she is afraid that she will not be brave enough to go on. But she didn't know that it wasn't that she couldn't grasp it at all, but that she lacked confidence. Because the only way to grasp the 'future' is to grasp the 'now'.
It wasn't until the last moment that Xue discovered that the car accident caused his "future" self to appear in the same space at different times, and he had been talking to his "present" self through "Mr. Little Days". "The person who writes the ending is myself at this moment, not waiting to be sentenced to death by my 'future' self!"
Xue decided that she would choose the path of her own destiny. For the last time, with zero time difference, Xue used his courage to get rid of his cowardly self and successfully wrote his own ending on 'Mr. Little Days'.