In one respect the terms happiness and unhappiness are just shorthand for the chief poles which orient the motivational system. It is not that we pursue happiness but that that happiness is the attainment of what we pursue. The system of motivations, or of desire which is almost the same thing, has far more consistency than that of happiness, even if the latter would seem to map more readily to brain chemistry. But this is only because happiness is seen as a state resembling more or less various experiences of pleasure or intoxication. In fact the varieties of motivation map quite well to the balance of the four fundamental hormones and neurotransmitters, oestrogen/oxytocin, testosterone, dopamine/noradrenaline, and serotonin. We can thus speculate that there are four independent systems or parties within us which each evolve and drive their own agendas. On a higher level they are reconciled by an evolved partitioning of life in a certain way so that each attains a proportional satisfaction. There is no separate system or self to effect this working division; it draws intelligence from the culture - you could say it computes in the cloud - it creates character but it has no self. Self only exists as a concomitant of motivations, and so we have different selves sharing the same body and memories and often with little need to communicate with each other. If consciousness is definitively intentional, self is definitively committed - to some system of goals, values, etc. It is not quite so simple, however, as self has no quantitative dimension - selfness is never a matter of degree but of something vaguely metaphysical. Selves can arise because they lean on an unmanifest reality.