Pyramids (but not Egypt)

Pyramids. Gorgeous in Egypt, tough on a speed session! Yesterday's pyramids involved one set of 500m/1k/2k/1k/500m with a negative split, and recovery jogs of half the distance we'd just run. Oof!
My times were set as follows:
500m - 2.24min / 1k - 4.48min / 2k - 9.36min / 1k - 4.46min / 500m - 2.22min

The first rep was easy. I love 500m! What a short sprint! Anything under 1k feels fantastic and short. I breezed through in 2.25min.
The next rep wasn't too bad either. I was running with a good friend who is around my speed - some days faster, some days slower - and it's great to be constantly challenged. We finished up in a time of 4.50min. Not the best, but it's well within my "5 second" buffer time I allow myself, so I was happy.
Onto the dreaded 2k rep! Just as any reps under 1k feel short and breezy, anything over 1k feels like a painful, never ending slog. This was arranged that we'd go out in one direction 500m then return to the start and continue in the other direction another 500m to make a round trip of 2k. At the 1k mark I was a couple of seconds off the mark, sitting at about 4.53min. I don't know what happened. My mind said yes, my body said I'm trying and my final time said nope. I crossed the line at 9.55min. That's 19sec slower than my goal time! In the second km I had dropped significantly slower.
It was disappointing. I just couldn't cut it physically. I don't know what feels worse - knowing I'm capable of running faster but not mentally pushing myself hard enough, or mentally pushing myself but not being physically able to increase my speed.
Fortunately, my slightly faster running friend was able to keep me feeling positive and keep me feeling motivated to keep up with her! The next 1k rep I finished in a familiar time of 4.50min. I think of my 1k personal best of 4.36min and wonder how I ever got down there!
The final 500m my friend all but flew, while I struggled to close the gap. She breezed through the final 250m as if it was her first interval of the morning and I staggered in behind her with a respectable time of 2.16.