Even from the ancient philosophical perspective, eudaimonia definitions differ. According to Aristotle, virtue and exercising virtue are central to eudaimonia, but also there is consideration given to external goods such as health, beauty, and wealth. Conversely (and for comparison), the Stoics did not believe external goods were necessary; for them, virtue was sufficient and necessary.
Aristotle believed that human beings gain eudaimonia when they develop their highest human functioning—rational thought and reason—and complement these with rational actions. That’s my super-condensed interpretation of Aristotle’s meaning of eudaimonia. If you’re interested in delving into the ancient origins of happiness and well-being, Aristotle’s Nicomachean Ethics and the Eudemian Ethics are a good place to begin.
In my mind and for me personally, eudaimonia would be something like: I could have all the medical knowledge (reason), medical ability, and empathy for patients in the world, but if I don’t put those qualities into action (work) by helping people, then I could not achieve true happiness.
Put another way, when I fully participate in intellectually stimulating and fulfilling work for the benefit of others, then I have found my purpose, my happiness, and my success as a human being.
Eudaimonia, sometimes referred to as eudaimonic happiness, has a yin/yang counterpart, or an “evil twin” depending on how you look at it, called hedonia or hedonic happiness. Hedonia is the sense of happiness induced by momentary pleasure or satisfaction and immediate self-gratification.
In my case, for example, hedonia could be the accolades of a colleague, a pay raise, or a new car (purchased because of the pay raise), all of which bring a sense of short-term happiness. No doubt that life brings a mix of hedonic and eudaimonic happiness, but what helps us achieve our purpose in life is the lasting happiness resulting from long-term goals and actions.
Thus, the ideal human quest to achieve well-being is accomplished when we strive for meaning and a noble purpose and go beyond self-gratification.