Happiness is a surge of dopamine, serotonin, oxytocin or endorphin. Dopamine triggers a good feeling when you approach a reward. Serotonin makes you feel good when you get respect. Oxytocin feels good when you trust, and endorphin masks physical pain with a euphoric feeling. Your happy chemicals turn on and off for reasons that are hard to make sense of until you know how they work in other mammals. Then it’s easy to see how they reward a mammal for survival-promoting behaviors. Your brain defines survival with neural pathways built from your life experience. You paved neural pathways with the happy chemicals of your youth. Today, it’s easy to feel good in ways that felt good before. When your happy chemicals dip, it feels like your survival is threatened. That’s why people rush to stimulate happy chemicals in ways that hurt them in the long run. This book shows how you can build new pathways in 45 days, to replace old happy habits with new ones. It’s not easy, but 45 days from now you will have power over your own brain, and it feels good.