Hey, let some air in there. Real life is not like the cheesy ads for laptop computers. You probably are not sitting on the beach with your computer. More likely you have been cooped up in your office all day.
Open a window. Can't open the window or you don't have one in your cubicle? Take a walk outside. It's good for you and what's good for you is good for your productivity.
You need sunlight and fresh air on occasion. Did you know Vitamin D comes from the sun? Take a walk and if anyone asks what you are doing smile and say "gettin' some D, just gettin' some D..."
When's the last time you went outside, breathed fresh air or saw sunlight?