Happiness in the ordinary sense is a sunlit state of the vital with or without cause. Contentment is less than happiness—joy of  peace or being free from difficulty is rather a state of joyful ´shanti. Happiness ought not to be a state of self-satisfaction or inertia, and need not be, for one can combine happiness and aspiration. Of course there can be a state of happy inertia, but most people don’t remain satisfied with that long, they begin to want something else. There are Yogins who are satisfied with a happy calm immobility, but that is because the happiness is a form of Ananda and in the immobility they feel the Self and its eternal calm and want nothing more.

Ref: Letters on Yoga – IV