Coping with Race Day Disappointment

I completed my 5th Sheffield 10K at the weekend and I admit that I was a bit disappointed in my time. I finished in 58.02, which is my slowest time for this race (and, I think, possibly my slowest time for any 10K race I've ever done, apart from Bolton Abbey, which doesn't count due to its chaotic nature - long queues and closed gates etc.) I had hoped that I might at least get close to what I got last year (54 minutes) but it just didn't happen. Part of the problem was me starting too far back. It meant I had a very slow start and took ages before I could overtake some slower people and finally start to get a bit of pace going. But that alone can't explain it. Another factor was my new trainers giving me pain in my toes. I can't work out why, but it MUST be these shoes as I don't experience it when I wear any other shoes. It didn't stop me running but I was conscious of it all the time and it probably stopped me pushing it as much a...