Read more of Brenda Ueland's If You Want To Write yesterday. Got to the "Art is Infection" chapter that I remembered from my first reading of it. Her assertion (drawing from various sources) is that one can easily identify Art because it immediately strikes you with a feeling; the feeling that the artist had when creating it. Thus, the artwork, be it music, painting, literature, is the medium through which this feeling infects you; the carrier of the infectious agent.
She couches her descriptions of this in religious terminology, drawing inspiration, I think, from Blake (to whom she refers often). In her description, it is the Holy Spirit that accomplishes the transfer. But even for the irreligious, her descriptions echo truly. They are Art, by her definition because they infect you with this idea that you can do creative things. More, that doing creative things is of great benefit to your soul.
She inspires me to write, to take time to do it every day even if no words come. I'm looking at NaNoWriMo, now, as an exercise in developing this habit. If I end up with 50,000 words at the end of November, great! If not, I hope to have acquired the habit of writing every day.