I can't do it at 4:30 AM but I can do it on the weekend. Really I just get going and zone out. Same thing I do on training runs outside. I let my mind wander to a million different thoughts. I don't sit there and think, "how far have I gone?" or "How much longer do I have to go?" The miles just go by. Periodically I sort of "wake up" and realize where I am.

Even with that, it's still much more of a chore on the treadmill than outside.