Saturday is my big race: 13.1 miles and it could go well or I could do very badly, mostly depending on the weather. This past Saturday afternoon I took off in 60F and ran 11 miles without a hitch and felt like I could easily do another 5 miles. Since then the temps have been in the 80's with higher humidity and I have gasped and wheezed my way to a walk every day at the 2 mile mark.
Two things: I don't think I will ever sign up for something like this again and I really am amazed that anyone voluntarily runs a full marathon. More power to all the "real" runners out there, that's for sure.