The great thing about having a race as a goal is that it keeps you going, despite setbacks and bad days and all. This weekend, I had planned to run 10 miles as part of my marathon training. I was out of town, so I needed to plan the run in advance since I would be on unfamiliar roads. Because of commitments during the day, I went running early at 7:00 a.m. It was still dark out, the temp was about 6 degrees, and a light wind was blowing. But I had a goal, and needed to stick with my plan. You do what you've got to do!
By the way, here's a great tool to determine mileage:
http://www.gmap-pedometer.com/
After putting in your location and zooming in as needed, click to start recording, and then double click on the map to start and to mark each turn in your course. Great for planning runs while traveling, and great for planning longer runs.