Simply put, your circadian rhythm is your body's internal clock. Operating on a roughly 24-hour cycle, it governs our sleep-wake cycle and plays a large part in everything from hormone release to body temperature.

This is not tired because you've had a long day. It's fatigue like you have the flu or like you are on chemotherapy. Some patients describe this as feeling like they have lead in their body or that they have no energy, like a dead battery.

What was wrong with me? I had turned the company around and it was continuing to grow. I was successful. Why was I so depressed and disoriented?

I'm not afraid of aging. I've been looking forward to my retirement years since I was in my thirties juggling four children and working two, part-time jobs. While others bemoan the toll that aging takes on their bodies and their lifestyle, I'm pouring over travel sites and counting down the days until I can pull out of the driveway in a brand spanking new RV.