Some vices miss what is right because they are deficient, others because they are excessive, in feelings or in actions, while virtue finds and chooses the mean.
Nichomachean Ethics
Datalinks
Ethical Calculus
The happy life is thought to be one of excellence; now an excellent life requires exertion, and does not consist in amusement. If Eudaimonia, or happiness, is activity in accordance with excellence, it is reasonable that it should be in accordance with the highest excellence; and this will be that of the best thing in us.
Nichomachean Ethics
Datalinks
Eudaimonia