Easy run + 6 x 100m strides

Today I was feeling pretty good before running. I ran after work at 7 p.m. with my brother in the Blasco park. The plan today was to do 9 laps in the park, and include 6 x 100m strides from laps 6-8 as usual.
The first lap was very slow in 6:10, I felt without energy since lunch was very light today, but We increased the pace a bit and felt better, looked at the watch in the 4th lap, We had 23:33, then did not look at the watch till the end of the run, but pressed the split button in the 8th lap in 44:48. We negatived split the run by 2:18, from laps 5-8, thanks to the strides, I did the strides longer than usual today, especially the first one. I felt good in the strides, but felt a bit sore in the quads. After the strides I felt better, but not great. Finished the 9 laps (8.1k) in 50:20, my brother finished some seconds back.
These days where you feel like crap is what move the needle so those need to be done.