Why is fate unpredictable?

Zhang Sanfeng, the founder of Taiji Chuan, said in the Complete Works: "The master has a life; Servants have their own lives; People have no life. People can go up and down, practice upward and fall downward. So all numerology is based on books, and all backbones are based on linen! " By his own admission, everyone has his own life. But he is a Taoist. He said, "My life depends on my absence. If I practice the elixir of life, I will become immortal. " He really lived a long life himself! His life is really unpredictable, and no one really knows when he died, probably soaring to eternal life! I have occasionally seen the life spectrum of the long-lived old man in Bama. At that time, the fortune teller didn't recognize him as a living 100-year-old man! So I think it is precisely because of the unpredictable fate that countless people want to try their hand on this road! Why is fate unpredictable? I think there are variables in this fate. Huangdi Neijing also said: "The qi of Yin and Yang is only based on image theory, not number theory." There is also an "uncertainty theorem" in science, right?