Here is a quote from a Pearl Izumi ad, that appeared in Runner's World magazine. I keep it on my refrigerator. "If you ran without sacrifice, congratulations. You just jogged. Running hurts. It always has. Wolly mammoths didn't just roll over onto a plate and serve themselves up to prehistoric man with fries and a shake. They had to be caught - and running down wolly mammoths was a b***h. But one with a purpose. It teaches us that good things do not come easy. It teaches us that we are capable of more than we think. It teaches us that hard work will be rewarded and laziness will be punished. Don't expect to learn those life lessons from running's shiftless stepchild, jogging. Next time you suffer on the roads or trails, suffer proudly. It means you run like a animal." For me, this helps explain the runs that turn out to be horribly difficult. Today you tried your best and the effort should not be frowned upon.