Interestingly the argument that fate is something that can be avoided and is not the overall influence on the life of humans is argued most strongly by Jocasta, who, of course, has a vested interest in trying to convince both herself and Oedipus that the prophecy will not come true. After Oedipus hears about the death of his father happening so long ago, he dismisses the prophecies, saying that they are "nothing, worthless," and Jocasta is quick to support him with the following speech when he mentions his fear about being married to his mother:
Why should a man fear? It's all chance,
chance rules our lives. Not a man on earth
can see a day ahead, groping through the dark.
Better to live at random, best we can.
There is of course intense irony in Jocasta's description of the condition of man being akin to a blind man trying to find his way ahead, as this is precisely what happens to Oedipus. In spite of Jocasta's words to try and convince Oedipus that he can avoid his fate, it is only at the end of the play, once Oedipus has realised who he is, that he is able to accept that his fate cannot be avoided:
It's mine alone, my destiny--I am Oedipus!
As he states who he is, he recognises that part of his identity is the fate that the gods have decreed for him, which cannot be avoided. Fate therefore in this play is something that cannot be shirked off no matter how hard humans try.
Prior to the ending of the drama, Oedipus would have seen himself as being able to defeat the powers of fate through his own free will. Oedipus speaks to this at different points in the narrative. He believes that his role as ruler is what will enable him to help his people's suffering in Thebes. He recalls back his own glories, such as solving the riddle of the Sphinx, as a part of this narrative. He believes that he has the capacity to defeat the fate that Tiresias sees as part of the leader's doom. Certainly, Oedipus believes that he has a fairly good chance at being able to change and/ or defeat the conditions of his own fate.
Then, the ending happens. Oedipus' thinking significantly changes. One can see this in his closing lines. When he says to Creon, "May fate guard you better than it did me," it is a condition in which Oedipus understands that fate and the power of the divine is larger than anything else he could generate. The sad revelation of a broken Oedipus is seen in the last wishes to his children: "Just pray with me that you obtain a better life than did the father who sired you." These lines help to convey that at one point Oedipus did believe that his own virtue and his own capacity for mortal greatness enabled him to defeat the powers of fate. Yet, the "sea of dire misfortune" that the Chorus suggests is a part of a narrative compels him to fully understand his own tragic condition as something inevitable, and as an unstoppable force.