Finding temporary and specific causes for misfortune is the art of hope: Temporary causes limit helplessness in time, and specific causes limit helplessness to the original situation.
Optimistic people generally feel that good things will last a long time and will have a beneficial effect on everything they do. And they think that bad things are isolated: They won't last too long and won't affect other parts of life.
The word 'happiness' always bothered me, partly because it was scientifically unwieldy and meant a lot of different things to different people, and also because it's subjective.