Staying motivated

"Laziness is nothing more than the habit of resting before you get tired." -Jules Renard

Today I ran a 5 miler that was supposed to be race pace (7:15/mile). Needless to say, I didn't finish in the 36:15 that I was hoping for. My problem is that I lost my motivation (and I started out too fast). Is it a good idea to just run without paying attention to the time, or should a runner look at their watch at each mile to see how they are doing?
My first mile I felt like I was going fast, but I didn't know exactly how fast I was going. I was thinking that if I didn't run that mile faster than 7:15 that this run was a failure & that I wouldn't be able to finish. I looked at my watch: 6:45. That was waaaaay too fast.
The second mile I tried to slow down, but it was still a little too fast: 7:07. After that I got tired. My third mile was a lot slower because I had been running too fast. I didn't realize how much I slowed down, however, until I looked at that dreaded watch: 7:39. That was waaaay too slow & I lost my motivation.
My legs hurt, my lungs hurt, it was hot, and surprisingly humid. So I walked. I walked for a total of 4:35 and ran 5:34 for the 4th mile. I finished up with an 8:16 5th mile.
This run wasn't a total loss. I learned that I don't know what 7:15 pace feels like. I need to become familiar with this pace so I can achieve my 45 minute 10K goal. I also learned that 7:15 will not feel as hard as 6:45 did. This gives me hope that I will be able to accomplish the task before me.
All in all, I think it is still good to keep track of your progress. Whether it's by your watch or by a pace group. I seem to remember a certain brother of mine that lost motivation as the 3:50 pace group started catching back up to us in Austin. We have to let our mind and body not give up when these progress markers let us know we aren't doing as well as we hoped. We have to keep going and come up with a secondary goal or figure out a way to achieve the primary goal of that run.
I'm just glad that this happened two weeks before my race and not on race day!

my runs (not like Charlotte's)
S - 3 mi, 25:23.42
M - 3.55 mi (tempo), 30:00
T - 3 mi, 25:00.79
W - 5.125 (1 mi warm up, 11x400 repeats, no cooldown), repeat times: 89.28, 90.56, 89.33, 91.06, 90.26, 96.48, 91.05, 95.98, 95.81, 95.33, 90.75
Th - 3 mi, 25:51.52
S - 5 mi (race pace, sort of), 39:54.22