Cure for Insomnia?

Those of you who have read Petite Bourgeoisie long enough know that I am an insomniac. But lately, I have begun running every day for about a mile, and my sleep problem has pretty much gone away on its own. I now feel really tired around 10:00 at night, and go to sleep by about 10:15, and wake up 9 or even 10 hours later. Could it be that exercising has cured my insomnia? Who knows? But it's lovely not waking up feeling tired.