Jocasta paid a very heavy price for her attempts to thwart her son's fate. By sending him away to be exposed to the elements and die, rather than allowing him to live to fulfil his prophesised fate, Jocasta was effectively denying the gods as well as setting up the situation for the prophecy to come into reality. By the choices she made, Oedipus grew up, by chance, not knowing who his true parents were so when he was killing his father and marrying his mother, by choice, he had no reason to think he might possibly be completing his fate. Ironically, Jocasta's fear of destiny was what brought it around and set her own fate. She believed she had disproved the prophecy and hence she rejected the gods and fate - "a fig for divination!" - only to learn that she was completely wrong and committed suicide for her punishment.
Jocasta did help set Oedipus' fate but he had a hand in it himself. The three flaws of his personality, rashness, quick and brutal temper and pride, lead him straight to his wretched fate. First of all, when he first heard of the prophecy, his rashness caused him to flee Corinth. But before this he had been told that Polybus and Meropé were not his biological parents. "Though perhaps I took it to heart more than deserved." If he had thought things through, Oedipus would have most