I've come to the conclusion that running (for me) is a thing of extremes. Either dip your toe in the water or dive in the deep end. There's no in-between.
This occurred to me yesterday:
I ran 6 miles in the morning on a track (I love running in circles, btw) wearing my vibrams. I ran differently. I stepped differently, and I felt graceful. Yes, I used the word graceful to describe my running. I was actually paying attention where I was stepping and how I was stepping.
I still enjoy an occassional 5k. They make me work hard. They're quick and painful. The beautiful pain.
...But, I also enjoy 60ks, 50milers and (attempting) 100 milers. They're definately not quick - a prolonged process.