I just heard from a Tanya tape on which Rabbi Jacobson says an extraordinarily all-encompassing principle from the Alter Rebbe- we are of-course nothing more though nothing less then desiring machines – of-course biologically, we have certain things that give us pleasure, so we desire them (say sex) we have certain things that cause us pain (say hunger) so we desire to get rid of the pain – emotionally, we desire camaraderie, hence we fear shame (being cut off from society); spiritually we desire goodness and kindness and feel repulsion at cruelty and evil – But there is a fundamental switch that either increases all our desires or decreases them – when we are happy, all our desires come to the fore (in fact, Chassidus speaks about this problem, for when in a state of happiness, not only do you have your soul desire, but also your selfish desires and hidden within the self is an ego that is easily enraged and in state of rage no man is incapable of barbarity, as we see in isis today) Conversely in a state of depression, sadness, all of our desires get minimized – which is why a depressed , sad person is lethargic – It is clear both states are not optimal, hence Kabbalah teaches, the only optimal state, is on one hand to be slightly depressed and reject any of your own desires, and on the other hand, be in love with God – for the nature of love is to fulfill the will of your loved one