I'm just a newbie here, but I wanted to chime in since your story is so familiar and say way to go on the run! I understand what you're going through. Long boring story, but I became physically unable to work out at all seriously for about 1 1/2-2 yrs. Though we'd go for hikes or ride our bikes, I'd pay for it afterward. Recently I decided I'm repaired enough to get my fat arse up and start moving again regularly. Well, the first couple early mornings were NOT easy, but I did it. Then I realized that not even a week into setting my alarm to get up, I was waking on my own - and even much earlier - because I couldn't wait to get outside! I think cherinyc is spot-on with her thoughts on endorphin effects.
Anyhoooo....have a SUPER ride tonight!