Reshaping your cultural identity (the folklore of can't), controlling arousal levels (mood swings), practiced mental imagery (renewed self-concept) and prayer relief (connecting with the supernatural) is the stuff of stamina which is what gets you over the finish line. This is why even seemingly most unlikely participant with inadequate training will themselves over the finish line.
Suffice it to say the Marathon is rigged to be a spiritual experience and Odyssey not a physical challenge. The body merely takes you through the labyrinth on race day with the road the cathedral. More then acclimating your body to heat or cold, you are acclimating your spirit to get real and to look inward and dig deep. It is totally mystical and paradoxical because you go inside to have this out of body experience As the body is kept busy (very busy), the mind is yielding and bending to what is now amounting to surrender as logic has taken a back seat to volition, and the spirit can finally soar unencumbered and free of self conscious inhibitions.