My personal experience: Sometimes you catch yourself in a state where you keep getting stuck in "fake work" mode no matter how hard you try to be productive. When this happens, take it as a sign that you may be approaching burnout (especially for those who try to cram insane amounts of work into the day), and GO RELAX / HAVE FUN (and don't feel guilty about it). Either way you're going to lose some "real work" time, but at least this way you'll be doing something that will help you refocus and be more productive the next time you sit down to work.