Sleep deprivation is a kind of chronic stress that impairs how the body and brain use energy," writes McGonigal in her book. "The prefrontal cortex is especially hit hard, and it loses control over the regions of the brain that create cravings and the stress response." In other words, a lack of sleep can cause you to make impulsive, unhealthy decisions that you wouldn't make otherwise. Getting enough sleep is perhaps the first step in gaining a sense of control over your life.