Answer: Various factors can change my prediction since I cannot control everything that happens in the world.
Explanation: When I make a prediction of something, I do it taking into account those factors of which I have control, but which can change since I do not control everything in the environment.
If I make a prediction about an event, it may be canceled because there may be rain, people do not go, or something force majeure happens. Predictions are never 100% accurate.