From my favorite book, The Art Spirit by Robert Henri:
…we must get rid of this outside feeling of looking in on art. We must get on the inside and press out. Art is simply a result of expression during right feeling. It’s a result of a grip on the fundamentals of nature, the spirit of life, the constructive force, the secret of growth, a real understanding of the relative importance of things, order, balance. Any material will do. After all, the object is not to make art, but to be in the wonderful state which makes art inevitable.