Not the ideal pacing strategy for a 6-mile run

What is wrong with this picture?

This graph charts my pace over this morning's run. I was doing really well until about Mile 3.7, and then ... well, I got tired.

Yesterday's workout had given me confidence that I could hammer out a pretty fast 6 miles today, so when I met up with the DART group, I started off at an aggressive pace. My splits for miles 1-3 were 7:20, 7:30, 7:18. The first part of Mile 4 was a 7:10 pace. But about halfway through the mile I realized that there was no way this pace was sustainable. I was running with Adam, but Chad, Sarah, and Jeff were behind us, so I decided to let Adam go and just walk for a bit. As it turned out, I walked for about a minute and a half, then took off at an easy pace as Chad and Sarah caught up with me.

Amazingly, my pace for Mile 4 had only slowed to about 8:30. Running with Chad and Sarah, I had regained my wind, finishing in 8:03, 7:51, and 7:28 for the final .37 miles. In the end, my pace for the whole run was still faster than yesterday. Today's average was 7:45, compared to 7:53 yesterday.

Not exactly the method I'd recommend, however, if your goal is a 7:45 pace. The record of today's run is below: