Why do we feel so bad when we have it so good? Your ever-changing, remarkably-dynamic brain consists of 86 billion cells with at least 100 trillion connections. It can store the information equivalent of 11,000 library books. So if it can manage all this, why can't it do something as simple as making you feel happy all the time? Psychiatrist Anders Hansen traces our brain development back to the early days of ancient man, explaining why humans as a species aren't biologically wired for happiness. The brain hasn't developed to feel good, but to survive by constantly planning for the worst - anxiety - and occasionally withdrawing as a self-defence mechanism - depression. He argues that improving our body literacy of our hunter-gatherer brains can help us to better understand our experience of the mental health issues so many of us face, and that a biological outlook on our emotional lives can help us to pinpoint exactly what makes us happy. By understanding where we've come from, we can learn to find a long-term sense of meaning and realistic, lasting contentment.