What's wrong with Predestination?

In knowing our future or not, why should it make a difference in our lives? If I go to on oracle and he tells me of some future event I shall be apart of. What should it matter? The only difference between me not going to the oracle is that now I know what the future event is going to be. Why would knowing change anything? I just may be a little bit more worried about the future but it won't change the event that's coming, because its the future. Even if the oracle told me about every single step and act that was going to take place after I left him, it shouldn't change a thing. It's predestination. What's going to happen is going to happen whether I know it or not, even the event of when I went to the oracle. So I would like to know, what's is so wrong about predestination?