This last Sunday I did the Cheshire Half Marathon.  Great temps (43F at the start).   Flat course.  Trained for it well.

Several weeks back I bought some hiking boots/socks, and have been doing some trail hikes to break them in.  The hiking socks are some kind of smart wool, and are pretty close to the same color as my running socks (which are not as thick).

So I accidentally picked out the hiking socks on Sunday morning, and didn't even think about them, until mile 11, where I was struggling to run.   I finished, but wasn't happy with my time.

When I got home I found that the hiking socks had crowded the small toes in my running shoes, and I had developed large blisters on the outside toes.  Natch.