Oedipus is very quick to anger and too proud to accept what is seemingly evident all along. His anger causes him to react harshly and without much logical thought. He makes a proclamation that curses himself without his even knowing it by ruling that whoever is the murderer of Laius shall be exiled with no help from any Theban.
He gets angry almost immediately when Tiresias refuses to give him the information he wants. Tiresias finally gives Oedipus the knowledge he can never take back: that he is the root of the plague on Thebes and the murderer he seeks. Oedipus is too proud to accept Tiresias' answer or to consider his words and investigate.
He also shows his rash temper when it is related how he killed Laius in what seems to be an early example of road rage! Laius and his party pushed Oedipus from the road, so Oedipus killed everyone in the party except one.
If Oedipus had better control of his temper, he might not have killed his father (fulfilling part of the prophecy), and he might have been less likely to make a blanket proclamation which ultimately caused his own downfall and exile.