The story goes that no matter how trashed you are, you'll always have enough in your body to out run a lion. Fight or Flight. Tim Noakes has written about it, me thinks.
It's an instinct which dwells inside each of us and if you can tap into that with your mind, you'd be amazed what you'd be able to extract from your body.
I'll be thinking of lions for the second marathon and see if that helps.
Love those mind games,