Running on the Edge

...you can experience no greater sense of freedom than what you feel when you run on a ridge that seems to hang in the air.  It's like running along the edge of a blade of a sword, taking care not to fall over one side as you accelerate with every step to leave the blade and the danger behind, though at the same time you don't want it to ever end.  There is danger, but you can think only of flying, of giving your legs the freedom to go faster and faster, letting your body dance as it keeps its balance.

Kilian Jornet, p. 86 in Run or Die