What is art?

I've had a pretty stressful few days, what with being ill and generally feeling "bleugh" so I cracked out the ol' paintbrushes and let my brain wander for a few hours....
Now I'm no Waterhouse, Cezanne, Dali, or whatever your tastes are, but after layer after layer of sketching this and that, I just painted over the lot and it made me feel better for doing it. Theraputic and whatnot.

I'm sure somewhere my second year art teacher would like it?
What do you think?