My worst run was my first 10-mile run from early February 2008. I was in the throes of the Hal Higdon Novice Supreme marathon training program (even though I had no plans to run a marathon). Here are the details from my run report that day:

The first three miles went great. I was going a little faster than I wanted to be (11:15 min/mile; I was shooting for 11:30-12:00 m/m), but my body wouldn't slow down. As I got into mile four, a snowstorm blew in. I was looking at whiteout conditions, and I could feel the air temp dropping. I kept on going, and made it through mile five without too much trouble. Halfway through mile six, things started to unravel.

The wind picked up big-time, and I was running into it for some pretty long stretches of road. I tweaked my route a little bit to keep me on some more sheltered roads where possible, but I could still feel the beginnings of frost-nip. I decided to keep on going, but I made sure my route took me near home pretty regularly so I could bail out if need be. To tell you the truth, the last four miles were on sheer willpower. My body was screaming at me to stop running and get inside. The air temp dropped down to about 17F (from 28F when I started), and when I went to get some water after mile seven, I found myself drinking water with a good helping of ice crystals. By the end of mile nine, I found that the cap had frozen to the bottle and there was a sheet of ice on the inside.

My best run? That's much tougher. There've been so many! I'll have to get back to you.