We tend to think of the universe as a stable system progressing from one state to another, methodically. This has been the dominant view for centuries. However, modern experiments have shown that the universe is basically unstable – yet is always observed to be stable. That is, looking forward in time there are innumerable possibilities, but looking backward in time we always see a coherent universe.
For whatever reason, we see only a coherent universe and not the quantum flux that is its underlying reality. This has interesting implications for faith, prayer and free will, but essentially the universe has two faces: an utterly chaotic quantum flux we cannot observe directly, and the highly ordered system we’ve become accustomed to.
For example, we see many properties of the universe as “laws”, such as the law that objects at rest will stay at rest. However, there is no such law: we have simply observed such perfect consistency in that regard that we infer the operation of a law. As far as the universe is concerned objects can move spontaneously, but as far as history is concerned, they do not (unless you consider miracles).
If consistency is only observed and is not a feature of the universe per se, it means that stability is something the observer imposes on the manifold possibilities of reality. We see a consistent progression of history because something about the function of observation demands it. Thus, if you go back in time and change something significant, you cannot alter the fact that observers after that moment must observe a coherent world. This is what makes time paradoxes impossible. People used to think that the universe itself was stable and therefore a temporal paradox would destroy its stability, but quantum mechanics says that only our observation of the universe must be stable and thus no matter what actions we perform in the past, it is impossible to destroy the stability of future observations.
As for the future we “came from”, it now exists as a separate potential along a branch in a parallel universe that is no longer real from the point of view of those who observed the change we made. A new and different universe new proceeds after the point of the change, to conform to the stability requirements of those who observed it. There is always a single history and uncountable futures. Perhaps you could even say that what we call historical time is the same as the reality of those who experienced it – that the fabric of our souls is made from the outcomes we observe, rather than a separate substance altered by such moments.