How much sleep are you actually getting? What was plenty before you started riding a lot may not be enough, given your now-higher amount of physical activity. Especially if you went from no activity to riding ten miles a day. The bigger your increase in activity, the more recovery (sleep) time you'll require until you get adjusted.

After a while though, you should start getting used to the extra activity and having more energy. I've been running and cycling regularly for about three years now, and never really noticed how much more energy I had until I lost it due to injury. I started training for a marathon, I got overzealous with my runs and gave myself shin splints. I ignored them for a while and they got really, really bad. So bad that I had to stop running and cycling because just walking became extremely painful. I was unable to exercise for about a month, and by the end of the month, I started to feel really lethargic. When I started running again, I felt sleepy afterwards for a week or two.

Hang in there, it'll work itself out.