Fresh wind in your hair. Bright sun in your face. The only sound you hear is the sound of nature and your feet tapping the ground, same rythm, for hours. Your watch beeps. 40km, and it feels like nothing. This is trail running.
Foot, hand, foot, hand, steady, steady, don't think, nooo! There you go, another 5 meter fall. Another finger cut open. But you go on, just 10 meters to reach the end of that line, you just need to get through that crux. It's like a puzzle, the way you use every muscle in your body to get there. But the most important muscle used in climbing is the brain. Turn it off, and you'll get there.