Just as a knife is "good" if it cuts well, a human is "good" if they perform their unique function well.
The Path to Eudaimonia: Virtue and the Golden Mean in Aristotle’s Ethics The Ultimate End: Happiness as Flourishing
We become just by performing just acts and brave by performing brave acts.
True happiness is not a temporary emotion but a state achieved over a complete life. The Nature of Virtue (Arete)
For Aristotle, the unique human function is the activity of the soul in accordance with reason .
Aristotle begins by stating that all human activities aim at some "good". However, most goods (like money or fame) are merely means to an end. The only thing pursued for its own sake is .