Man's fate is decided by heaven? Or is it up to people?

According to the eight-character theory of fate, birthdates is predestined (the birthdates of a baby born by caesarean section is not decided by himself). But there is a life that changes with the heart and life. No matter what a person's fate is, as long as he devotes himself to good deeds, he will be rewarded. Good is rewarded with good and evil with evil is an unbreakable truth for thousands of years. From this perspective, man's fate is still up to him.