I ran a planned pace of around 9:40 per mile for most of the race. At the halfway point, I felt really confident in the pace and felt very relaxed. My thoughts at that time were reflections on how well the training program seemed to come together. Basically, the pace was much quicker than my longest training runs, but much slower than the shorter weekday runs. Supposedly, after several weeks of tapering, it was all supposed to come together...essentially a fast pace on a long run. I even had in my mind that maybe I was running too slow? I recalled a comment on twitter "If you feel good while running, don't change anything".
This seemingly managable pace continued to mile 20 when, all of a sudden, I began to experience some cramping in one calf. Not too long after that, both calves began to cramp. I continued, slowing some and managing it, and then I had to stop and stretch. I really didn't know what to do. I had never experienced any leg cramping while running before now. The quick stops to stretch seemed to alleviate the cramping enough to keep moving forward. Before long, I had to stop again.
Looking through my GPS data for the last 6 miles, it looks like I stopped more than a dozen times to stretch. I even had to stop just a couple hundred feet from the finish line. I went from averaging 9:40 pace for the first 20 miles, to an 11:30 pace for the last six miles due to the many stops. Basically, the cramping cost me about 9 minutes off of my marathon time that seemed in the bag through Mile 20.
Crossing the finish line, the reality really set in. I had just run a marathon. The finish time was 4:24:06. It was done!