“In part positivity reflects the brain’s reward circuitry in action. When we’re happy, the nucleus accumbens, a region within the ventral striatum in the middle of the brain, activates. This circuitry seems vital for motivation and having a sense that what you’re doing is rewarding. Rich in dopamine, these circuits are a driver of positive feeling, striving toward our goals, and desire. This combines with the brain’s own opiates, which include endorphins (the runner’s-high neurotransmitters). The dopamine may fuel our drive and persistence, while the opiates tag that with a feeling of pleasure. These circuits remain active while we stay positive.”

– From “Focus: The Hidden Driver of Excellence” by Daniel Goleman http://amzn.to/1OqxnWe