The Oatmeal has a very good comic about life, particularly the lazy introvert's life who has to find ways to cope with him/herself and the world.
"The Terrible and Wonderful Reasons Why I Run Long Distances."
It's impressive and I think captures the essence of what plagues many (if not most) of us introverts.
I used to run as well, although not such long distances. Perhaps if I stuck with it I may have. But even regular short runs did provide not only health benefits, but a peace of mind hard to come by anywhere else. The longer the run, the more accomplishment you felt, the more satisfied you were with yourself.
I may be projecting a little, but I think a lot of our lives would be better if we weren't so sick of our self. Maybe it's just me, but if I'm not constantly busy, and improving myself in some way, then my demons return and torment me with how far away I am from my ideal self, regrets, fears, and constant reminders of my failures. Exercise, especially running, is probably the best way to keep those demons at bay.
I'm sure alchohol and drugs work, although I haven't tried those as a coping method. Something tells me it's not a great idea. Lately I've been trying to keep my mind occupied. But I don't think that's working out well--I seem to have grown afraid of boredom.
I've probably said too much. Introverts don't typically share their innermost thoughts, but I'm willing to try this as an experiment. So consider this part 1. The Oatmeal's comic seems a pretty good introduction (Did I mention I was lazy?). Part 2 will come whenever I feel like it. Or never. Who knows.