Good weather, bad run

The weather was perfect for my long run yesterday. Unfortunately the spirit was willing but the flesh was weak. What was supposed to be a 10 mile run ended up being a very slow ~9 mile run. At that point I was just exhausted and didn't have the energy to push on. I can come up with all kinds of excuses for it but they would just be cop outs. It really doesn't matter why anyway. The bottom line is that I didn't meet my goal and I'm annoyed to no end by it. I just hope this isn't an indication of how the race will go in 3 weeks.