Watson had been drinking a bit more than he'd originally meant to. He wasn't depressed, precisely. He'd lost his job and gained the most frustrating man to live with on earth as a roommate. Still, his life wasn't completely awful. He'd had a very enjoyable Christmas. And his work at the clinic was rewarding enough.
Strangely enough, Holmes didn't seem to interrupt his shifts at the clinic as often as he did the hospital hours. Watson theorized that Holmes was quite deliberate in his attempt to get Watson fired, and knew that charity clinics would not let go of someone as easily as a large hospital would. Besides that, it was a clear mark of dominance; that Holmes' time was far more important than Watson's, even though others were willing to pay Watson for it. Holmes was marking his territory.