There exists a unified model of the brain as a combination of a quantum and a classical mechanism(s). The classical part of our brains measure and classifies. The quantum part of the brain collapses the quantum possibilities into a single point, creating a perceived reality and giving us creativity, free will, and "ah-has!". The paradox of the brain is that we experience separation from others where there is no separation. The driver for this separation is that the quantum/classical interfacing point is experienced in a transcendent state, and we cannot "see" this connection.
An analogy is the false logic loop created by the question, "have you stopped beating your wife?" It can be answered with neither yes nor no. Instead it is solved by a transcendent wave of the hand, for we either don't have a wife or we are not beating her.
I think the experiencing of sadness, in the same moment of coming from a desire for happiness, awakens the transcendent mind to the true nature of love. Love stands outside of the wife/beating and sadness/happiness logic loops. It is transcendent, and only is indirectly apparent when we realize the paradox of emotion. To seek happiness as a respite from sadness is like seeking an ending to our beating the wife. It cannot happen. What can happen is our realization that the duality of sadness/happiness is an illusion, and love stands outside of this illusion.