What phrase did you repeat to yourself when the going got tough? The wheels came off? What got you through the pain of that last tough race and you prevailed on top?
For me, it was from Balto. He is cold, time running out when he remembers Boris' quote "A dog cannot make this journey alone, but maybe a wolf can..."
https://www.youtube.com/watch?v=ucfHDO4k9gM
I just repeated to myself, "maybe a wolf can" with the occasional mid race howl to motivate me and lo, BQ at Houston marathon.