Oedipus is not the victim of fate alone. His tragedy emanates from himself. He is a headstrong man who acts impulsively and in haste. He loses his temperance and allows his emotions to go unchecked. Oedipus destroys his balance and therefore becomes the perfect tragic figure.
Throughout the play, Oedipus acts impulsively. He doesn't stop and look at both sides of an issue; he just acts with his first instincts. When he hears the Oracle tell him of his horrible fate he doesn't stop to think about it, he acts immediately and flees from Corinth. He doesn't consult his parents and tell them of his decision, he just runs away. This is the type of behavior he exhibits throughout the rest of the play.
Now that Oedipus if King of Thebes and has already unwittingly completed the prophesy of the Oracle he appears to be a just and benevolent ruler.
But with the arrival of the plague and the decree from Apollo ordering revenge upon the murderer of Laios Oedipus becomes headstrong once again. He immediately orders the exile of the murderer and pompously claims "Then once more I must bring what is dark to light." This hubris is just the beginning of his tragic downfall.
As Oedipus tries to find the murderer he consults the seer Teiresias who tells him bluntly to stop looking because "there's no help in truth." Oedipus arrogantly ignores his advice without stopping to consider what he has said. This is Oedipus' flaw, his hamarteia. Here he loses the qualities of the good man except courage, which is misdirected without temperance, justice, and wisdom. The downfall of Oedipus is now apparent. He has become completely unbalanced and therefore must return to the mean.
As Oedipus continues on in his quest for knowledge he is getting...