#1: My 5k PR was 15:54 although I was probably in 15:30 shape and my shorter PRs indicated I should be more like a 15:00 guy. The 15:54 was my first college 5k and I ran it on the double after a decent 1500m. The rest of that year and the next year I ran about 8 or 10 times between 16:00 and 16:10 which was way below my capacity...I wasn't finishing races tired, just feeling like I pussed out every time. The last meet of my second year in college I decide I am going to go for it and go with the leaders in a decent sized regional meet. The better people in the meet were 14:20-14:30 guys. I figured I would probably die but still PR, and maybe get a huge PR, but I was excited about the idea of at least trying to race the leaders rather than just settling in the middle of the pack and going for a time. My training had been picking up and I think my coach was expecting a decent PR for me but I was a lowly walk-on and never got much attention.
We go out running fairly even 70s and I was tucked in there through the mile (4:40) and almost 2000m. At 2000m (6:03) the top 3 got away and everyone started passing me. I went out the back door real fast and fought to hang on for a PR but 80s felt like 60s and I ended up in 16:03, on the last lap my teammate telling me to "kick with the mountain man" (some heavily bearded dude). I think my last lap was 78 and I used to be a great kicker closing races near 60 in high school.
Needless to say, my coach was really pissed.
#2 Parkersburg Half Marathon. I was in decent shape, but had not raced in a year because I'd been injured but I was regularly running 10 to 20 mile runs at 6:00 pace without feeling blown out. I estimated that I could do a half at around 5:40 pace and my longest distance PR at the time was 10 miles at 57:17 which I'd done on the track as a tempo a couple years earlier and I was in at least that shape.
It was very hot and humid that day and I suck in the heat.
I go out "easy" feeling great and surprised when I go through the mile in 5:30. I slow it down a little to keep it under control and the next mile is 5:50-something but it is uphill so I was expecting that. I died hard on mile 3, struggling to hit 6:00 and figure that I'm done so I will just try to hang onto 6:00 pace and make it a good run. Mile 4 is 6:30 and I'm totally falling apart and thinking how am I even going to finish. I slow down to 7:30 pace which feels like a tempo run but is manageable, then catch a couple of guys with elite bibs who died and packed it in. We conspire to find a shortcut to the finish so we can watch the leaders but even with the shortcut making it a 10 mile run, we don't get there before the winners and it felt like a tempo run, but was probably 65 to 67 minutes.
About a year later I vindicated myself in my only other half marathon running exactly 5:40 pace. I was at 55:04 at 10 miles but it was San Diego and the last couple miles are uphill. I was going for sub 55:00 at 10 miles and hang on, so even though it was a pretty good bonk, I was close to my goal there...