The Gods Again!

Oedipus was a tale that I was familiar with, though when reading it after the Iliad I noticed some interesting things.

In my mind, I started drawing a comparision between Patroclus and Oedipus. Both were fated by the gods to have tragic ends, and both overstepped their bounds, resulting in the end that befell them. Patroclus by attacking where he shouldn't have, and Oedipus by declaring vengance and promising to make the person who killed the former king an outcast.

Oedipus was once again a character fated by the gods to have a tragic end. And while he doesn't die like Patroclus, what happens to him is worse in a way. We know that Oedipus is told by Apollo that he will kill his father and marry his mother, but that he chose to marry anyway and indeed this fate came to pass.

But does this truly mean that it was fated to happen? Couldn't Oedipus have chosen never to marry, thus breaking the hold that fate had upon him? COULD he have made that choice and still saved the city?

And if it was fated, can Oedipus be held accountable for the outcome? Did he really have a chance to do differently, and should he have felt such sorrow over the fact that he was the one that killed the king if it was fated to happen by the gods? The point that I am making is this:
With characters like Patroclus and Oedipus as examples, can any character in these epics really be held accountable for their actions if they are fated to happen? And if they can, how do you differentiate between acountability and what is the will of the gods? I don't have an answer to this question, and I wonder if those that wrote the works that we now read did either.

P.S. I commented on Lucy Beth's post.