Excellent question. I've been looking for an answer for years, and only recently found one that works for me, and, I believe, would work for most anyone.
The key is physical exercise. Not only does it strengthen your body and controls your weight, but it also relaxes you and does wonders for insomnia too, among other things.
The problem, of course, is that physical exercise requires certain amount of motivation, dedication, and time, but, unfortunately, all of these things are completely allocated to my start-up. Sure, I can find some free time, but I'd much rather spending it programming, not sweating. Anyway, I cannot devote myself to two conflicting tasks - it tares my psyche apart. So I say to myself: "I'll go to the gym in an hour... in two hours...", until it's too late, so I say "I'll go tomorrow", knowing full well that tomorrow will be the same story.
And then I found a gym, which pays me in cash for each exercise ($10/hour), on condition that I stick to the agreed upon schedule (say, a couple of hours each morning). I can change the schedule only one month in advance (and provide a good reason for changing it), and if I break the current schedule, I pay a $1000 fine. Talk about motivation!
I've been doing that for 11 months now, I lost 20 pounds (and don't intend to stop there), my heart arrhythmia is history, my eyes and hands aren't sore anymore, I fall asleep like a baby, I feel 10 years younger overall, and my hairdresser swears she can't find my bald spot anymore (scientifically implausible, I know, but still)!
And to top all that, the exercise requires no mental effort to speak of, so I can still think about my start-up while exercising, and, as it turns out, it's much more effective than sitting in front of a computer. In fact, I got some of my best ideas this way.
By now you're probably wondering where you can find such a crazy gym. Actually, there are many of them - they are called the cleaning contractors.
Okay, yes, if you want to be technical about it, it's a part-time job cleaning stairs and offices, but for any practical purpose I care about, it is a gym that gives me a motivation like no gym ever could. So why won't you give it a try too?