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.
—Gretchen Rubin in The Happiness Project