I believe it is all about right brain vs left brain.
My hockey analogy is when you play, if you start to think, you are screwed. Every play will be too late, and you'll be on your ass. You practice for years using the left brain, which looks after skating, shooting etc, where to go and when, --muscle memory.
You right brain can now take over and creativity, and at times, magic arrives to take you to another level. You are in a zone and anything is possible.