What did Oedipus do wrong?

The play opens with a scene in which Oedipus and Jocasta learn that Polybus is dead. Oedipus takes the news in of Polybus's death without showing even the slightest sign of grief. The moment actually becomes a near triumph, as Oedipus believes his doubts about prophecies have been confirmed. He is now convinced that prophecies are useless. He even says, "But now, all those prophecies I feared-Polybus packs them off to sleep with him in …

…basically identifies himself as someone who must search for his identity. Oedipus is famous for his skill at solving riddles, so he is making his own life into a riddle. In the end I see his major downfall as not letting well enough alone. Through his intense search he finds out the truth, which eventually ruins his life and the life of his wife and mother. His worst nightmare has in a sense come true.