I am doing the Dopey and so my biggest fear (outside of completing the races injury free of course) is that I will end up hitting that mental wall. I hit it this past year at mile 21 and really don't want to experience that again.
So outside of a safe journey for everyone...my fear is that mental wall...I never want to see it again.
Sorry, I missed a coachable moment....
This year when you start to feel that feeling come on, fight! First, slow up a bit, but DO NOT fall out of your norm. i.e. if running continuous, try dropping 30-90 seconds a mile off your pace but do not yield to the "if I could just walk" voice. Likewise, if run/walking, fight that loud voice saying, "just let me walk another 30 seconds, I promise, this will be the only one"
Yielding is losing as far as the wall go (and yes I know there is a point when you cannot keep the fight going). Work with all you fiber to not yield to the need to lose and walk. Great little games that MAY work are,
Running to the next corner
Running to the next street light
Running to the next stripe in the road
Running to the next crack in the road... These are getting shorter and shorter but the point is to give yourself a goal to make then pushing it out once you make the goal.
Tying an imaginary string onto a runner 15-20 feet in front of you and letting them pull
Dedicate each mile to a friend or family member who helped you get to race day.
Smile

Shake out your hands

and take a deep calming breath can relieve some of the stress causing you to want to stop.
Turning up the music or otherwise just trying to drown out the surroundings and pull your focus into a single spot on the road (like looking through a straw) will help keep the evil thoughts at bay.
One tool we coach folks as we try to get them into a mental zone is wall sitting. We have folks stand about 18" from a wall, and sit into the wall so the thighs are parallel with the floor (making sure we practice good form and keep the weight over the heals and not the toes) and hold that pose for 3 minutes. We talk about the various sections of a marathon while we work through the clock and have the runners use many of the mental tools I have discussed. The runners are not allowed to look at a clock during the exercise. The trick to the exercise is that we stay there for 5 minutes, not 3. What this does is reenforce the mental side of the game.