Oedipus cannot escape his destiny. He cannot assume complete control over his future. Other forces, be they fate or Gods, will always have some effect on the outcome of his life.
This, naturally, is true for all of us. There is always a will to take control of our lives, but there are limitis on our ability to achieve complete control of our personal fate. Outisde influences are a fact of life.
Oedipus is like us in this way, unable to achieve the corol he seeks but unwilling to five up his efforts toward that end. No matter what his intentions, "Fate and the gods, however, have other things in store for Oedipus."
Aristotle, in his Poetics, states that poetry is more philosophical than history because it is more universal. History, for Aristotle, may consist of improbable actualities but poetry must consist of probable inactualities, or universals of human nature. According to Aristotle, Sophocles' Oedipus Rex is the ideal tragedy.
What is universal about it is not so much the specific events -- it is not actually common for people to murder their fathers and sleep with their mothers -- but rather the human reactions to the events. In other words, the way in which Oedipus becomes arrogant once he has obtained power, and the way fate overrides human will are both universal despite the events being unusual. The choruses often express the most universal aspects of the play, drawing forth from unusual events general conclusions applicable to all people, such as:
So while we wait to see that final day,
we cannot call a mortal being happy
before he’s passed beyond life free from pain.