Again, I think it was the heat more than anything. I got off about two hours later than I had planned -- overslept, ran an errand, and then had to go back home to get my iPod after driving out to the park without it. It's pretty funny, though, 'cause miles 15-16 weren't so bad for me this time, but they were killer when I did my 16-mile run. I hope miles 17-18 are fine for me in 2 weeks, when I do my 20 mile run. I'm really looking forward to next week's long run, since it's only 10 miles. I can practically do that running backwards now.
I feel fine now, so I think as long as I keep sticking with it, the endurance will come. I'm going to try to work in some bicycling into my routine, which should help with endurance, too.
Looks like the marathon is 10 weeks out. I think I'll be fine. Slow, but fine.
In other marathon news, I enjoyed watching the women's marathon on the Olympics tonight. They ran an entire marathon in less than half the time it took me to run 18 miles. Inspiring.