When running is good, it's great. When it's bad, it's terrible!
So before I go out for a run I try do my bit to ensure it goes well, I like to get a decent nights sleep the night before, I eat well through the day (I run after work), I try to keep mobile as much as my desk job allows and drink plenty of water through the day. And 9 times out of 10 this seems to work for me as I really enjoy the run, my times are constantly improving (i'm around 4 minutes faster for 5k than I was at Graduation in April) and really feel like I'm "getting somewhere".
But last night it felt terrible. 5 minutes into the run I was shattered and I have no idea why. I couldn't control my breathing, my legs felt heavy and, forgive me for being crude, but I was sweating buckets! I staggered to my finish but I did not enjoy that run at all.
Isn't it strange how for some reason on a given day your body just says "Not tonight son!"