Full Idea
A good person is bound to do whatever he does well and successfully, and success brings fulfilment and happiness.
Clarification
'Happiness' is the Greek word 'eudaimonia', also sometimes translated as 'flourishing'
Gist of Idea
A good person is bound to act well, and this brings happiness
Source
Plato (Gorgias [c.378 BCE], 507c)
Book Reference
Plato: 'Gorgias', ed/tr. Waterfield,Robin [OUP World's Classics 1994], p.105
A Reaction
Not how we would see it, I guess, but this is the Greek idea that a good person is one who functions well. Anyone who functions well is probably having a good time.