My my! Maybe I should have asked if there were anyone who didn't play guitar, lol!
As to relaxing, it is that. It's a great stress reliever. I also see playing as a fusion of two vastly mental functions which usually find themselves isolated from each other: mathmatics and emotions.
I feel my music comes not from just within my own mind, but from another Source. Just as the guitar is an instrument, so am I. Music isn't on the page, and to a degree, not in the heart either, or not solely so. It seems to come from "somewhere else", through me. The purpose of training is to allow this to happen, and when true inspiration strikes, it is an awesome experience. Suddenly, all the effort and errors seem to vanish, and it is not so much me playing as it is me being played. It's almost as if I am just an observer of some wonderful and cosmic process. When the poetry comes as well at the same time, I feel it as a holy thing because I know it is greater than the sum of my parts. Inspiration is the sacrament of my religion, and I am refreshed after tasting it.