Here is a nice excerpt from a piece on Dathan Ritzenhein, who has struggled with never ending injury but keeps plugging away.
His internal fire and love for running is what keeps the torch lit. Its inspirational to me simply because I enjoy being able to run as it reminds me of a side of me that I really like.
check it out
You've been at this a long time. Is the training enjoyable enough in itself or is it chiefly something that leads to the races that are the payoff? DR: I really enjoy training. That's one of the biggest things I missed in that whole time away. I couldn't train at all. I don't particularly care to cross-train, but I would rather cross-train than do nothing, but there were a few periods between the surgeries and the infections and all of that when I couldn't do anything for six weeks at a time. You know, I'd never really had that (before). I could always usually do something. And I realized that I like training, I like to be fit. I like the everyday satisfaction of having done something that most people can't do. It was something I missed a whole lot. So I really do enjoy the training. I don't particularly like it when I'm out there doing quarters (400s) and it's super hard, but I like the satisfaction of having done it every day.
That's what sometimes separates people who always run and always train and people who maybe move on in life and do something else. I think I'm a lot more likely to be someone like Joan Benoit (Samuelson), who keeps going forever, just because I actually really like it, as opposed to someone who stops and never runs again.