Responsibility

One of the notable themes in Medea is, "Human beings are responsible for their own misfortune."  The idea is that actions, whether they were deliberate or not, come with consequences. These consequences must be recognized and dealt with.  

All of the characters in Euripides Medea fail to take responsibility for their own actions.  For example, Jason abandons Medea.  This causes cataclysmic events to himself and those around him. However, Jason never acknowledges that he is, at the very least, partly to blame for the results that occur.  Instead, he wishes they never happened.  

Medea accuses Jason for being at fault for the death of their children.  Even though Medea herself was the murderess, she insists that because Jason broke his oath he drove her to kill their sons.  She says that it is ultimately Jason's fault.  Medea never accepts any blame for what she does.  

Jason and Medea's actions lead to their own misery.  Although, they refuse to accept the consequences that their actions bring.  The entire play consists of Medea searching for revenge.  She does get her vengeance.  But everything intended to make Jason feel horrible also makes her feel horrible.  By the end of the play, both characters have made themselves miserable. Neither Jason nor Medea hold themselves accountable for their own misery, a misery in which they themselves ultimately caused.  

Medea by Euripides is a fantastic example of the theme, "Humans are responsible for their own misery," due to this.