Every day we all engage in a surprising number of habitual behaviors. Many of them, from brushing our teeth to driving a familiar route, simply allow us to do certain things on autopilot so that our brains are not overtaxed by concentrating on each brushstroke and countless tiny adjustments of the steering wheel. Other habits, such as jogging, may help keep us healthy. Regularly popping treats from the candy dish may not. And habits that wander into the territory of compulsions or addictions, such as overeating or smoking, can threaten our existence.