There is something amazing that happens during a run that seems like a total loss. If you keep going, it gets better. Sometimes MUCH better.
This happened to me today to some degree. I began running my normal slow pace. I felt fine. Lap 1 (1.1km), lap 2, lap 3, then I started feeling worse. Lap 4, lap 5 and I felt really bad. This is where I always stop at the motorbike and grab my water bottle. I drank for a minute, walked around a bit and started running again. BAM, back in the groove. I had energy and felt great the next 4 laps. I even ran 7 sprints of around 300m each at sub 5 minute pace. I felt awesome. I don’t know how much longer I could have run tonight, but I’m sure I could have done 3 more laps before my energy and feel-good state changed.
If your run is sucking for a bit, take a walk, drink something, and then run again when you feel like it. You might be surprised.
What happens I think, in most cases anyway, is that the fat burning mechanics switch on and you have energy again. When you have energy, you relax. You glide. You run smooth, light, easy, and therefore, faster. There is nothing quite like it. Some people call it a second wind. I call it fat burning. If you can train your body so you’re burning fat immediately as you start your runs or other exercise, you’ll be able to go for a longer time and feel great during your session.
Give it some time and see what happens. Don’t ever stop a workout after a mile or two if you intended to do 5 or 6. The entire run might turn from junk to amazing, and it’s just due to fat burning.