This drama basically started off with both main lead how they meet and all those. Then the girl ( Han Fei ) had a accident and died which the boy ( Wu Jing Hao ) regretted not to save her as Han Fei met him before the accident. So 10 years later, Jing Hao is a doctor and he went back 10 years ago, about 3 to 4 months before the accident and he tried ways to stopped it, Along this journey, he started to know more about Han Fei.
But on the day of the accident, Jing Hao saved Han Fei with his life. He left a letter for Han Fei about him coming back from the past and how he tried saving her So the drama skipped to 10 years later where Han Fei is a a doctor , went through what Jing Hao did, went back to 10 years and then she saved him and they both lived happily ever after.
( P.S. I am mentioning partly of the story )