Yes, this is why I don't fret about my 7-12 mile rides in the early AM, or in yesterday's case, because of weather. These rides always have 1-2 good hills and frankly, the only flat rides I can do are either across town and back (10 miles), an extension of this that has one hill, but we still call it the "flat ride," and is 18-20 miles, or riding to the bike trail in a longer way.
I woke up at 4 AM, so since I was up, I went to spin class at 5:30. Only one other person was there, I guess they were all up late watching the Red Sox. I am glad they won, but I can't alter my schedule for that! I am meticulously rigid about my sleep, exercise, and nutrition schedule, because if I am not, bad things happen.