Slower than fast, faster than slow

The goal of today's speed session was to run 1k intervals at an increasingly faster pace, with a 1k recovery in between.
I am not good at pace. Especially when I don't have my pacing watch on! It was a 500m out and back so I only had the chance to see how I was going at the halfway mark and the end point.
I can run my hardest on a rep. I can run my hardest across continuous reps and get them all within 5sec of each other. I can also do a nice easy pace for those longer runs & recoveries. What I am decidedly not good at is starting a bit slower than my hardest. I just don't know what that feels like.
The goal I was given was to run subsequent 5k reps of 5.07, 5.02, 4.57, 4.52, & 4.47. But on the first rep out I paced myself too fast and I couldn't get it just right. Fortunately, I buddied up with another gal going my pace and we passed the time beautifully. I had to remind my energetic companion that I didn't have much breath to spare for talking on the reps, but otherwise it was just like having a regular conversation with intermittent 5min gaps in speech.
Lap 1: 5.01. Oops! The good thing was the knowledge that if I kept to the same pace I'd be right on for the next lap.
Lap 2: 5.01
Lap 3: 4.56
Lap 4: 4.52.

I didn't have time (or energy or inclination) to go to lap 5. In truth, lap 4 just about did me in. My saving grace was that my coach elected to run the last rep with me. When I gasped out to him that my goal was 4.52 on the last lap, he encouraged me to go a bit faster (my 500m split times were continuously 2.30min) and preceded to pace me that extra edge towards the finish line. Had I not soon sighted the finish, I don't know if I could have mentally kept that pace going.
I could hear myself sucking in air raggedly as my coach calmly jogged beside me, not even having the decency to look short of breath. But I was so excited! He had set me a challenge to keep up to him and finish my last rep in at 4.52 and by golly, that's exactly what I did. I may not have gotten around to completing that final rep, but it was a successful morning nonetheless.