Plato ( PLAY-toe; Greek: Πλάτων Plátōn, pronounced [plá.tɔːn] in Classical Attic; 428/427 or 424/423 – 348/347 BC) was an Athenian philosopher during the Classical period in Ancient Greece, founder of the Platonist school of thought and the Academy, the first institution of higher learning in the Western world.
You may find more from Plato on Wikiquote
The belief that unhappiness is selfless and happiness is selfish is misguided. It's more selfless to act happy. It takes energy, generosity, and discipline to be unfailingly lighthearted, yet everyone takes the happy person for granted. No one is careful of his feelings or tries to keep his spirits high. He seems self-sufficient; he becomes a cushion for others. And because happiness seems unforced, that person usually gets no credit.