Thus, we see the problem with prophecies in more...creative media. Unless it is either just a possibility (as in, not 100% certain) or extremely vague, they tend to completely undermine any sense of dramatic tension. If a prophet says something will happen, and he's never wrong, then no matter what you do, that thing is going to happen. You have no choice in the matter. You might have free will, but it doesn't mean a thing, since the wheels of prophecy will move despite your own actions; every choice is rendered meaningless.
It is, essentially, a predestination paradox.