Only if I don't sleep well is it difficult for me to get up at 5:10 and hit the road. I have done it on little sleep and it isn't worth it.
However about a year ago I remember telling my wife one morning as I returned from my exercise ride, "You know it says alot about your lifestyle if the high point of your day is over by 6:30 am."

Don't imagine that I don't have good days, it's just that I really enjoy getting my ride in!