Once I skip one or two meals, work long hours, or stay up late, my life starts spiraling out of control. So I live on a fixed schedule now, which includes three hours of exercise per day:
* One hour of swimming at 7AM; this forces me to get out of bed on time, and makes me hungry for breakfast.
* One hour of rowing at 5PM; this forces me to stop working, and makes me hungry for dinner.
* One hour of running at 11PM; this forces me to stop whatever I am doing that evening, and gets me tired for bed.
(In addition I have hundreds of small rules: never go shopping alone, the bed is only for sex and sleeping, dinner must take at least fifteen minutes to prepare, ...)
It does take a lot of time and self discipline (and monitoring by others), but it sure helps me to keep my life under control.