This is how I felt both yesterday and on Thursday. On Thursday I was running intervals, and not any kind of intervals but the worst kind (for a Captain Slow like me) - 2 min intervals at 'high' speed. It was 10am, I hadn't had breakfast and just done an hours BodyPump. I struggled (and swore) a bit, and my leg didn't really feel all that good, my breahting was all over the place.... but I did all the six intervals I set out to do! I stepped of the treadmill feeling very tired and very happy.
Yesterday I did 5k's at threshold pace, also after a 60 minute Body Pump session, and even if I wasn't as tired as the day before it is quite mentally tiring running at a constant pace which is higher that your comfort pace. I plugged in my iPod (well, iPhone), cranked up the volume and tried to diverse myself with music. It worked and I finished the 5k without any major problems.
So, what's the morale of this story? You might not like running while you're at it, but you'll love it when you're done!