Personally, I hate when destiny gets used in fiction, largely for the reasons that Bob points out. As someone who's been writing fantasy since I was . . . 12 I think, I've used destiny as a plot device twice in my entire life: once when I was really young and didn't know any better, and once in a completely different way from usual. The prophecy was not something related to the world, but the character received a personal revelation because he just happened to visit a wise, elderly priestess to ask for a blessing for a friend who'd been injured earlier and he gets this very potent, but vague personal prophecy, the purpose of which he is told is not to let him know what's going to happen, but to basically tell him that things are going to happen that are going to change his life and if he doesn't pay attention and watch for it, the choices that should be his will all be made for him.
And, although I haven't written this far in yet, the the prophecy and destiny thing never becomes more than a personal conflict between him and a character who evolves into his personal nemesis. His destiny isn't to save the world, or change it in some way. Everything he does that gets him known to the world is both due to his own personal efforts and completely unrelated to the prophecy. The resolution of the prophecy happens in private and nobody knows anything about it except the main character, his closest friends, and his nemesis. My thinking is that the whole purpose of his prophecy is not to tell him what to do, but to prepare him for the time when he can either take control of his personal destiny, or let it fall into the hands of others who want to use him. It's not to tell him what to do, it's to give him an awareness enough so that he can make his own decisions.
Sorry, rambled a bit. I just wanted to suggest another way in which destiny can be played with. But the point is, played straight, destiny is a cheap way to strong-arm characters into action. You shouldn't use destiny unless you're putting a twist or something on it.
And, although I haven't written this far in yet, the the prophecy and destiny thing never becomes more than a personal conflict between him and a character who evolves into his personal nemesis. His destiny isn't to save the world, or change it in some way. Everything he does that gets him known to the world is both due to his own personal efforts and completely unrelated to the prophecy. The resolution of the prophecy happens in private and nobody knows anything about it except the main character, his closest friends, and his nemesis. My thinking is that the whole purpose of his prophecy is not to tell him what to do, but to prepare him for the time when he can either take control of his personal destiny, or let it fall into the hands of others who want to use him. It's not to tell him what to do, it's to give him an awareness enough so that he can make his own decisions.
Sorry, rambled a bit. I just wanted to suggest another way in which destiny can be played with. But the point is, played straight, destiny is a cheap way to strong-arm characters into action. You shouldn't use destiny unless you're putting a twist or something on it.