Durning my morning fly-over of blogs, I saw this article by Matt Fitzgerald referenced by Liza Howard on her blog.
Like most (all) writing, Matt's article is well worn. Anton K has discussed (read: defended himself against the less accomplished runners who always want to give him advice about mileage, etc) the fact that running the long distances that he does gives him confidence in races. People always point to a breakdown in their body during long events but in reality it's a gap in mental drive that most come to the edge of and don't have the confidence or faith to jump that gap, so they walk, worry, and otherwise give up. Matt Carpenter's phrase "when it hurts, speed up" is simple yet poignant. What I've noticed, in myself as well as many others, is that when we get to that point where we want to walk because it hurts/doesn't feel good, we tend to stop taking care of ourselves (fueling, hydration, etc.) and we spiral down from there.
Two polar examples are Tony at Leadville last year and Geoff at WS. One had the mental capacity and confidence to continue taking care of himself and continue running, albeit at a slightly slower pace, until he cleared that gap and was back on track. The other got to that point and stopped taking care of himself and, well, dissolved into a heap.
The ultimate outcome from years of training and stretching that limit of mental drive can be seen in someone like Meltzer. He can now train physically less and maintain the results because he has trained his mind both in its capacity to handle the stress and in the way it works with his body. When I asked him how long my long runs should be while training for hundreds, he said, "you know that running hundreds is about being stubborn". Granted, he's not saying lie around on the sofa and just force yourself to finish well. What I took from that conversation was that once you know how to get the body through the bad situations in a hundred (and, trust me, they are hideous), you don't have to beat the body to hell by running 50 mile training runs.
I follow the mental training that Fitzgerald talks about in the article. On almost all but the most simplistic runs I focus on keeping that connection of how I feel and how I perceive myself as feeling (likely why I don't talk much in group run settings). I still breakdown in races mentally and have talked myself into slowing/stopping but with each race I become more intuitive, which translates into being stronger.
I like to think of it as meshing the mental strength with physical strength so they are in tune with one another as opposed to solely building confidence. Raw, abundance of confidence can lead to your downfall in a long race just as easily (and often quicker) than lack of confidence. There needs to be a blend of an objective, realistic assessment, physical ability, and confidence. With one of these missing, you won't hit your potential.