Happiness is acquired by virtue, and hence by our own actions, not by fortune.
In Nicomachean Ethics, Aristotle regards the highest form of human good as eudaimonia, which would be roughly translated as happiness in English. He further argues that in order to achieve such happiness, one should act with appropriate virtues over the course of an entire lifetime and live a good life.
To stretch the term of ‘happiness’, Aristotle defines happiness as the ultimate purpose of human existence. However, his term of happiness completely differs from the modern conception of happiness, that is, seeking pleasures, having fun with friends, enjoying a drink etc. And it is not something that can be gained or lost in a short time, like pleasurable sensations. It is the ultimate value of your life as lived up to the moment, measuring how well you have lived as a human being. Therefore, one cannot conclude if he/she has lived a happy life until it is over, just as we would not say that a book was “a great book” when we are halfway through. As Aristotle describes: “for as it is not one swallow or one fine day that makes a spring, so it is not one day or a short time that makes a man blessed and happy.“
Aristotle also presents his ‘doctrine of mean’. He states that every virtue lies in between two extremes which are excesses of qualities that make up that virtue. For instance, when he gives the example of courage as a virtue, he also mentions that it falls between cowardice and foolhardiness. And he further examines these qualities to conclude that living a good life requires one to be temperate.
What is the most interesting part of his arguments is his idea of flourishing as a person: “The same actions, then, are the sources and causes both of the emergence and growth of virtues and of their ruin; but further, the activities of the virtues will be found in these same actions. For this is also true of more evident cases, e.g. strength, which arises from eating a lot and from withstanding much hard labor, and it is the strong person who is most able to do these very things. It is the same with the virtues. Refraining from pleasures make us become temperate, and when we have become temperate we are most able to refrain from pleasures. And it is similar with bravery; habituation in disdaining what is fearful and in standing firm against it makes us become brave, and when we have become brave we shall be most able to stand firm”.
So, flourishing is both a mean and an end. We strive to flourish by acquiring virtues and molding ourselves accordingly. However, walking through this path itself is a virtue and requires good actions. Therefore, there is a continuous cycle of happiness in pursuing the good life. And this thinking concurs with his idea: “Happiness is an activity, not a state.”