I've been running for a year or so now. I ran a marathon, and no, I am not freakishly skinny. That question out of the way, I think a lot when I run. The mind wanders. I often think I should carry a tape recorder, and have written a few poems while running just by repeating the words over and over to the rythm of my footfalls.
I like to run at any time of day. In the morning you get to see all the details of how the neighborhood wakes up. I know when differnt houses wake by their lights. I wave at the guy who delivers table cloths to the resteraunt down the street. The cafe workers clean the tables in the sidewalk as they set them out.
In the afternoon, there are a lot more runners. They wave at you, and some run in groups. There is always someone who passes me at the end of a longer run and I draft off them, thinking about how I know I've already beat them in pure milage.
At night, it is nice to just shower after a run and collapse.
All of it, though, is about being stubborn. In the end, it is pure stubbornness that gets you out of bed at 5 am, that laces up your shoes after a hard day at work. A wise person once told me that getting started was the hardest part, from there on you're just heading back home.