I suppose it is good once in a while to run yourself into the ground, then force yourself to keep on going. That happened to me on Saturday, twenty miles into a 25.6-mile run in Forest Park.
I started at the Leif Erickson trailhead (at the top of Thurman Road) but turned off almost immediately, for almost a mile on the sharply uphill Wild Cherry Trail. After that it was basically a loop, more than 14 miles north on Wildwood and more than 9 miles south coming back on Leif. (Other connecting trails were Dogwood and Springville Road.)
I took the whole run slowly, but I already had a lot of miles on my legs from earlier in the week, and it got hard for me shortly after getting back onto Leif. Fortunately, Leif is (relatively) flat and (mostly) downhill in that direction. So I was able to keep shuffling along the whole way, with only the occasional walk break. It was mentally tough, though. I was taking it mile-by-mile, treating each new whole number on the every-quarter-mile mileposts as a little victory.
Eventually I finished, in about 4:35. My feet hurt quite a bit, but have gotten much better since.