A translation with loose paraphrase:
The demon of acedia— also called the noonday demon— is the one that causes the most serious trouble of all. He presses his attack upon the monk about 10:00 am and besieges his soul until 2:00 pm. First of all he makes it seem that the sun barely moves, if at all, and that the day is fifty hours long. Then he constrains the monk to look constantly out the windows, to walk outside his cell, to gaze carefully at the sun to determine how far it stands from dinnertime, to look now this way and now that to see if perhaps one of the brethren might appear from his cell. Then he instills in the heart of the monk a hatred for the place, a hatred for this very life itself, a hatred for manual labor.
-Evagrius Ponticus, 4th century monk
Updated for the 21st century student:
The demon of acedia— also called the noonday demon— is the one that causes the most serious trouble of all. He presses his attack upon the student in the period prior to lunch and besieges his soul until the third hour after lunch. First he makes it seem that the clock hardly moves, if at all, and that the day is fifty hours long. Then he constrains the student to look constantly out the window, to fuss with his pencil, to remove the ink-and-spring guts from his pen, to draw three dimensional boxes in the margins of his notes, to ask to use the bathroom or to blow his nose or to get a cough drop or a TUMS from the office, to constantly recalculate the number of minutes or seconds until the end of the period, to look up from his text and glance now this way and now that to see if any other students also happen to be looking up from their books, and if so, to snicker about something. Then acedia instills in the heart of the student a hatred for school, a hatred for learning, a hatred for intellectual things.