Stop, Laura, Stop!

I did not want to go for a long slow run today. After a beautiful weekend of running along the beachfront with friends where it was less like running and more like floating on air...how could I go back to dogging it solo for the next 90 or so minutes?
By the time I dragged myself I knew just what I'd do. You see, I have two runs to get done this weekend - LSD and sprints. Why not combine them for a long slow...sprint? What better way to pre-fatigue than to slog a couple of k's beforehand?
So out I went, mentally changing my route every couple hundred metres. In the end, I did a nice easy jog around the park, starting flat-side first. This lasted 4k. I climbed a hill for the next km (it's a long hill!), recovered down the other side, and...blast off! Away I went with my sprints.
Too easy, right?
So it would seem. In km 2 I started to get twinges in my shins. Nothing worth stopping over, but mildly concerning all the same. Not concerning for this run, but concerning because I shouldn't be feeling any twinges in my shinny shin shins.
Luckily, that went away when I hit the hills. Onto sprints! And you know the weirdest thing? I really am liking sprints. I think it's because it's mentally so easy. First, it's just 20min. 20min!!! Seriously! Second, I don't count the recovery parts in my mind. And third, I mentally break it down by thinking of it as mini-challenges.
Mini-challenge #1: 2x 90sec intervals. No worries. After the first one, there's just one left!
Mini-challenge #2: 4x 60sec intervals. Again, just a simple countdown. And after 90sec, 60sec is nothing! Too easy. I might start getting tired by the 2nd one, but then there's only two left!
Mini-challenge #3: 4x 30sec, 4x 15sec. I'm not even sure if this could be classified as a 'challenge'. Afterall, that's a grand total of 3min of sprinting. And it's so short I barely get going before it's over.

I was happily cruising through the sprints. I got down to the 30sec intervals, my mind chanting out "Go, Laura, Go!". When out of the blue, my body cried "Stop, Laura, Stop!". The back of my knee flared up in pain. Nothing super serious, but more than concerning. I had less than 5min to go in my sprints - less than 5min! My mind desperately wanted to finish it off. The pain wasn't that bad, just a bit of a red flag.
I stopped. I walked home. It was so, so hard to do that. Much harder than if I'd finished the sprints at a gentler loping gait. But live to run another day is a creed I follow.
Don't worry all you concerned readers: as soon as I stopped running the pain went away. It made it all the harder to call it a session, but I did.

Total time: 50.42
Total distance: 7.90km
Total elevation: 354m
Avg pace: 6.24

90sec rep/recovery x2: 5.11/6.14 \ 5.38/6.54
60sec rep/recovery x4: 5.24/6.48 \ 5.37/6.50 \ 5.12/6.16 \ 5.05/6.18
30sec rep/recovery - incomplete. Live to run another day.