The human body is a marvel.
Every day, it goes through a stunning number of invisible functions and processes in an effort to keep you functioning at optimal levels. These activities are governed not only by a "master clock" located inside the hypothalamus portion of our brains, but by trillions of other clocks living inside the cells of our body. Together, these clocks work to keep our "circadian rhythms"—defined as "physical, mental and behavioral changes that follow a daily cycle"—in sync. Keeping these internal clocks calibrated is key to your health and well-being. They're complex, and their effects are wide-ranging. But we do know there are some common behaviors that throw these internal clocks out of whack, rendering them less effective at doing their No. 1 job—making you the healthiest human being possible.
Source : http://www.stack.com/a/3-ways-youre-sabotaging-your-bodys-internal-clock-and-why-its-making-you-feel-terrible