Half of your baseline mood is genetic. And if yours runs low, you got lucky. The people born with naturally cheerful brains coast through life. Their default setting is good enough, so they never have to develop the habits that make happiness a craft. So when real adversity hits — and it always does — they are completely unequipped to handle it. The rest of us have to train. We learn to manage sleep, exercise, attention, relationships. We get good at moving negative emotion from the limbic system into the prefrontal cortex. We build the practices because we have to. To us, happiness is a sport. By age forty, the trained-up gloomy person is an elite happiness athlete. The naturally cheerful one is an amateur with luck. I'm not saying this just from research. I come from very gloomy stock. I've worked my whole life on these habits because I had to. Without them, I'd be sad and sick; with them, I'm doing better at sixty than I did at thirty. This is the same principle as alcoholic genetics. Half your tendency toward addiction is inherited. People with the worst genetic risk who never drink are not addicts. People with no genetic risk who drink hard can still wreck their lives. Knowing the genetic tilt means you can pay attention to the habit. And paying attention is how you win. The gloomy who don't train end up sad. The gloomy who train end up better than the cheerful who don't. If joy doesn't come easily, discipline will — and discipline is something the lucky never had to build. So if you're naturally gloomy, congratulations. It's harder for you. That means you'll be better at it. Happiness is a sport. And you'll be one of its best athletes.