Some of us may be quite aware of the pie chart on the front of Sonja Lyubomirsky's book, the How of Happiness, which shows that genetics control most of our happiness.  However, genetics are not destiny and this article, by Emiliya Zhivotovskaya,  is a nice concise explanation of how our genetics and our experiences interact to produce our "happiness".

How does happiness work in the body? Here is where the mystery starts: if DNA is the powerhouse of the cell, then is it true that your happiness is set at birth?  Not exactly. Yes, the genes in your DNA have a role. For example, there are genetic differences among people that affect the production and transportation of serotonin, a neurotransmitter that modulates anger, aggression, and mood. Thus you may be more genetically prone to depression and experiencing less happiness than some other people because of the genes that control your serotonin system. But believing this is the whole story is a recipe for learned helplessness. Truly believing you are doomed by genetics may prevent you from ever taking steps to make positive changes in your life. Happiness and life-satisfaction levels are only partially pre-programmed. Making yourself happier is not as futile as trying to make yourself taller.