Eudaimonia (happiness) is the purpose of life, its end. Areté (virtue) is the means to that end. Humans have a natural inclination to all that causes pleasure, but not all pleasure causes happiness. The “vulgar” individual will seek pleasure to be happy (Nicomachean Ethics, book I), but will fail as virtue is the only way to achieve it. It also causes pleasure in the individual as it acts with virtue, but virtuousness can also lead to its corrupted version (vice) if it is exercised in excess.
For the Stagirite virtue can be divided between intellectual and moral virtues. While intellectual virtue can be taught by “experience and time,” moral virtue must be exercised to become a “habit”; one does not become virtuous from nature (Nicomachean Ethics, book II). In order to become virtuous, one must overcome that “natural inclination” towards all that is pleasurable (human nature), and control it by reason and measured restraint. It implies using our human differential characteristic, which is rationality, in order to choose right between two extremes. This notion of balance (the Golden Mean) between “excess and defect” must guide human action towards real happiness, not mere pleasure.
“Excess and defect are characteristics of vice, and the mean of virtue.”