Compulsion for Flight

I've never been able to really put into words what running is to me in the psychophysical sense. At times I have called it addiction however I understand the definition of addiction to be a practice or action which affects normal function and when removed causes physical and/or emotional withdrawal symptoms. To a degree this holds true for running, however I find it rather easy to stop running without feeling withdrawals. That said, when I start running again after a period away, it takes only a couple of runs for my body to be compelled to continue. When I have stared running again, I get a feeling like I feel today where while I am sitting I actually feel my body wanting to get up from the sitting position and run, to feel that sensation of moving quickly and often moving up a hill, feeling of movement, not just any movement but one that is smooth and powerful. Then, when I think of this I feel grateful for the gift of motion. Not so many people are able to feel powerful and efficient in such a natural form of movement.  Then, despite how smooth, efficient and powerful I can feel when I am very fit, land movement is still cumbersome compared to flight. I cannot imagine how that would feel, to fly under your own power.