So I brought in my colored pencils and ink pens and a lavishly illustrated book on birds, and started spending my lunch hour doing practice pieces.
Practice pieces are just copying someone else's art in order to 1) learn how they got the effects they got, 2) hone one's freehand drawing skills, and 3) have a bit of relaxed, fun art time without worrying over how it turns out. Since it's not your own original art, it doesn't matter how it turns out.
The book I've got at work is "Birds: Their Life, Their Ways, Their World" by Christopher Perrins, and the illustrations are by Ad Cameron. The book covers birds from all over the world with hundreds of lovely illustrations covering identification, habitat, breeding, feeding, behavior, etc.
I normally do one piece during each lunch hour, sometimes two if things are going well. I sketch the bird lightly in pencil first, then either finish with pen-and-ink, or water-soluble colored pencils, or both. It's changed my whole attitude towards Lunch Hour. Now, staying at my desk is something I look forward to.