Happiness is a sensation experienced when two or more harmonious energy systems unite or polarize.
By corollary there is pain in forcible seperation between two harmonious energy systems. So some persons don't enjoy sweet taste and some others don't enjoy bitter taste - because the sensory currents present in their taste buds do not match with the frequency of sweet or bitter tasting food products. When one is sick, the sensory currents recede due to increased levels of toxicity in the body so the best of foods do not taste good. We celebrate when birth takes place and remorse at the time of death of a beloved. In birth there is union and in death forcible seperation.