I really can't believe it, but I made it throught the 5K, running the whole time, and no stopping. I'm used to running on an even track and there were hills on this course. Holy crap, I thought I was gonna die at a couple of points. Thanks everyone for your encouragement and advice, it helped!
This might sound cheesy, but when I was running I would think of the kids (guys younger than me) storming the beach at Normandy in WWII and how completely hellish that must have been. I figured that if they could do that, against all odds, I could finish the damn race. The cheering spectators helped too!
There were about 11,000 runners for both the 25K and the 5K - a huge crowd. It was great!