According to this video you're future is already predicted.
https://www.youtube.com/watch?v=YycAzdtUIko
It's not just that video of course, the implications of Einstein's general relativity changed our whole concept of what reality was. The fact that time wasn't a kind of esoteric notion but an actual dimension orthogonal to the other three changes everything. It is possible, according to general relativity, for one person to in someone else's past. If this is the case it would seem that our future is predetermined.
The term block universe is often used to describe this, as opposed to the universe being like a movie, it's like a canister of film. The future, past and present, or beginning, middle and end of the film are all already there. We're just experiencing the change from one frame to another, or another way to think of it is a book is already written beginning to end, regardless of the page we're reading.
What I think might even be more fascinating is if we are currently in someone else's past, it doesn't feel like it. What we are currently experiencing as our present, making decisions, thinking, anticipating future events, is all currently inalterable history for someone else. This is where things get tricky as past, present and future tense don't apply in the same way, but that people in history are currently experience what we consider the past as their now. Even you from the past of a few minutes, years, decades ago is still experiencing what your currently think of as memories.
A theory I have to explain this is we are living every moment of our lives simultaneously. It makes sense when you think of us not as a bunch of individual moments but as a long object, from birthday to death in space-time. If the universe is one big four dimensional block, why do we experience it as though there were a flow of time? Perhaps that is just an illusion and we are experiencing all points in time simultaneously, which is what one would assume looking at the structure of space-time. The only reason it seems like there is a now, is because it's all now. The point in your timeline where you are reading this is happening right now, always.
So why does it feel like time is moving forward, why does our now never seem to be before another now, only after? Because the space-time block's construction must obey the laws of physics. In the same way that a crystal is formed, each molecule finding it's location determined by the location of the molecules before it. We think about the laws of physics as what dictates the laws of motion, but there really is no motion. Instead the laws of physics dictate the method of construction of 4D space-time. An analogy might be a finished Sodoku board. The numbers can't just be put there at random, they have to be in their place according to a set of rules. Keeping this in mind think of 4D space time as containing the dimension of left right, up down, back and forward, and past and future. Now think of the molecules as being stacked on the past, so future locations of particles are determined by the location of past particles, similar to a Tetris board where top shape locations are determined by bottom shape locations. We have memories of the future we're just facing the wrong direction to see them.
Hopefully this made sense, it was my attempt to explain how we know our futures are predestined but it feels like we're living in a single moment. I of course may be wrong, things like Everett's multiple worlds theory if proven two would have a huge influence on this world view, and even aside from that the nature of consciousness has no need to conform to my hypothesis.