I really did look like this yesterday. I worked diligently all day long, consumed twice as much coffee as usual, and by mid-afternoon was wearing long sleeves... Because, due to my intense concentration on writing, I hadn't realized the house had cooled down a lot and I needed to turn off the air conditioner. Brrr!
But even if I risked an overwhelming electric bill and frostbite, at least I was productive. I was intensely focused. (Me! Intense about something!) As Barbara Hannay says, "head down." Yep, that describes it.
This, I think, is the way a good writing day is supposed to be.