In Medea, both Medea and Jason take matters way too far. They were once happily married, but then Jason became ambitious for more power. He decides to throw aside Medea and marry a woman of preferable rank who will give him more power. Unable to be content with the power he already possesses, Jason's "enough is never enough" attitude is what sparks the tragedy. Medea's reaction is what fans it.

Medea is distraught by her husband's betrayal and decides to take the ultimate revenge on him by killing his new bride, Glauce, and his children. The latter hurts her, since they are her beloved children too, but her bitterness outweighs her love. Medea takes things much too far, leaving both herself and Jason alone and childless, with no hope of reconciliation.

The Nurse embodies the theme of moderation. She says she would never wish to be a "great" person as Medea and Jason are, and she criticizes her mistress's over-the-top reaction to Jason's behavior. In the Nurse, Euripides is championing the idea of self-control and humility as the best way to approach life, as it allows one to avoid the bloody, senseless tragedy of Medea and Jason.

In the period in which Euripides' Medea was composed, one of the most important virtues was considered to be self-control or moderation (sophrosune). This was considered a particular virtue of the Spartans, but also one in general possessed by Greeks rather than barbarians and more characteristic of men than women. Moreover, lack of moderation is considered one of the vices to which those with excessive power, such as tyrants were particularly prone. This sentiment is expressed by the nurse who says:

… Ruthless is the temper of royalty: […] How much better to live among equals. […] Let me decline in a safe old age. The very name of the "middle way" (21)

Both Jason in his unmoderate desire for power and Medea in her desire for revenge are examples of lack of sophrosune resulting in disaster.