The unhappy person resents it when you try to cheer him up, because that means he has to stop dwelling on himself and start paying attention to the universe. Unhappiness is the ultimate form of self-indulgence. When you’re unhappy, you get to pay a lot of attention to yourself. You get to take yourself oh so very seriously.
Happiness is always a byproduct. It is probably a matter of temperament, and for anything I know it may be glandular. But it is not something that can be demanded from life, and if you are not happy, you had better stop worrying about it and see what treasures you can pluck from your own brand of unhappiness.
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.