Throughout my preparation for this, my first marathon, I've been reading What I Talk About When I Talk About Running - a memoir by novelist Haruki Murakami.
As a (very) amateur writer and runner, it is perfect reading material for me right now - lent to me by my boss when she heard I was training for the marathon.
I identified really strongly with his attitude to running. For Haruki, it seems that running is a meditation and a discipline; a way for him to tackle his life as a writer with a newly found physical and mental strength. It doesn't seem to be about success in its pure sense; rather his running is a way for him to challenge himself, to better himself, and to find out more about himself. Through his running, he remains true to himself.
All of these things, I identified with. They're exactly what I talk about, when I talk about running.