...you go to the doctor, and he prescribes a treatment for low-light deficiency syndrome!
you get it when somebody makes an "arrow in the knee" joke.
you accidentally call your boss a "Jarl".
you look towards your feet and see three bars floating in the air. One's red, one's blue, and one's green.
you look up and suddenly know which direction you're going, what sort of buildings are nearby, and if any enemies are about.
you put Oblivion in for the first time in awhile, see that you have a lot of ingredients, and wonder where the nearest mixing station is. Even though your character has a mortar & pestle!
.