Happiness is always a by-product. 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. 

Robertson Davies

As one of my professors once taught me, being smart is just being low on the dumb scale. So perhaps being happy is just being low on the unhappy scale. (aka Happiness and Unhappiness are made up of the same "stuff" it is just how much of the "stuff" you have.)