Happiness is an achievement brought about by man’s inner productiveness and not a gift of the gods. Happiness and joy are not the satisfaction of a need springing from a physiological or a psychological lack; they are not the relief from tension but the accompaniment of all productive activity, in thought, feeling, and action. Joy and happiness are not different in quality; they are different only inasmuch as joy refers to a single act while happiness may be said to be a continuous or integrated experience of joy; we can speak of “joys”(in the plural) but only of “happiness” (in the singular).
Happiness is the indication that man has found the answer to the problem of human existence: the productive realization of his potentialities and thus, simultaneously, being one with the world and preserving the integrity of his self. In spending his energy productively he increases his powers, he “burns without being consumed.”
Happiness is the criterion of excellence in the art of living, of virtue in the meaning it has in humanistic ethics. Happiness is often considered the logical opposite of grief or pain. Physical or mental suffering is part of human existence and to experience them is unavoidable. To spare oneself from grief at all cost can be achieved only at the price of total detachment, which excludes the ability to experience happiness. The opposite of happiness thus is not grief or pain but depression which results from inner sterility and unproductiveness.
Erich Fromm (1947) Man for Himself: An Inquiry into the Psychology of Ethics