Full Idea
A well-constituted human being, a 'happy one', must perform certain actions and shrink from other actions. In a formula: his virtue is the consequence of his happiness.
Gist of Idea
A good human will be virtuous because they are happy
Source
Friedrich Nietzsche (Twilight of the Idols [1889], 5.2)
Book Reference
Nietzsche,Friedrich: 'Twilight of the Idols and The Anti-Christ', ed/tr. Hollingdale,R.J. [Penguin 1972], p.48
A Reaction
A nice reversal of basic Aristotle, though Aristotle does say that the truly virtuous person is happy in their actions. Treat unhappy people with caution!