Do not train so hard, that you strain yourself to the extent that you might have to pull out of the event.
With sore heels, or the heel spurs, I am planning to pull out of the full marathon with just a month to go. Have not been able to put enough miles on the legs, for the training.
Injury is so depressing that I run a day, and rest for next two days, further ensuring that I walk less. I have had IT band and knee injuries before, and they rehab process and keeping oneself away from the trails was so frustrating, when that is the thing you most badly want to do.
Biking/swimming/Gym cross workouts are some of the ways to avoid the body fitness level from going down.