I am finding that it is the same with "going". I mean covering ground on my feet. The more I do the more I want to do. I'm in the middle of running 100 miles this week and I realized that 100 miles is not that far. So in a few weeks, after I recover from Reach the Beach, I'm going to do 120s. When I can go on a 20 mile run/hike on saturday, a 19 mile long run on Sunday and the a 17 mile double Monday and still feel pretty good Tuesday and Wednesday I want to work closer to my potential. I'm base building. I'm not supposed to pop out a 5:29 mile on the grass with the boys cross country team after a full workout with the girls team.
If you want to see a play by play of my runs the last few years read my running log. If you read my workouts they have the highs and low all documented. From tearing my plantar and the crying during my first 18 mile run to setting the WPI 10,000 record. It's all there.