Couple of days ago, I followed a link on Less Wrong to Paul Graham's essay on holding a program in your head. I can't program, but I get the analogy: you think of playing videogames for hours, you think of obsessive fixations, in yourself and in other people. I've always said that the best way to read a book is in one continuous session, and maybe just before or after watching the movie version.
This feels big, a large, non-cryptic truth that ties together a dozen or so fragmentary insights I've had. It's the reason why a sudden, unplanned day off, like a sick day or classes suspended due to storms, is sweeter than the weekend or regular time off: you're geared up for several hours of effort, then reprieve. You could play videogames all day, or whatever turns you on.