Book excerpt: Are you optimistic or pessimistic? Glass half-full or half-empty? Do you look on the bright side or turn towards the dark? These are easy questions for most of us to answer, because our personality types are hard-wired into our brains. As pioneering psychologist and neuroscientist Elaine Fox has discovered, our outlook on life reflects our primal inclination to seek pleasure or avoid danger -- inclinations that, in many people, are healthily balanced. But when our "fear brain" or "pleasure brain" is too strong, the results can be disastrous, as those of us suffering from debilitating shyness, addiction, depression, or anxiety know all too well. Luckily, anyone suffering from these afflictions has reason to hope. Stunning breakthroughs in neuroscience show that our brains are more malleable than we ever imagined. In Rainy Brain, Sunny Brain, Fox describes a range of techniques -- from traditional cognitive behavioral therapy to innovative cognitive-retraining exercises -- that can actually alter our brains' circuitry, strengthening specific thought processes by exercising the neural systems that control them. The implications are enormous: lifelong pessimists can train themselves to think positively and find happiness, while pleasure-seekers inclined toward risky or destructive behavior can take control of their lives. Drawing on her own cutting-edge research, Fox shows how we can retrain our brains to brighten our lives and learn to flourish. With keen insights into how genes, life experiences and cognitive processes interleave together to make us who we are, Rainy Brain, SunnyBrain revolutionizes our basic concept of individuality. We learn that we can influence our own personalities, and that our lives are only as "sunny" or as "rainy" as we allow them to be.