EDIT: I changed the image at the bottom because sonntagsleerung is exactly what I'm trying to describe here.
My sister and I have an informal yet surprisingly well-developed set of theories concerning The Dread. Most of the people I know are aware of The Dread, even if they have never called it by that name. It's not universal, but it's a commonly experienced by people who work regular schedules and/or go to school.
"The Dread" is the feeling of dreading going back to work (or school) you get on weekends or vacations. When it hits, you know it. You stop enjoying whatever it is you're doing and are preoccupied with the resumption or your work or school week.
The Dread theory posits that, the longer the time off, the longer the duration of The Dread. You might think that it would hit the day before returning to work regardless of the length of the time off, but The Dread does not seem to work this way. If it's a regular two-day weekend, The Dread might not kick in until Sunday evening. If you're on week-long vacation, it might start on Saturday morning and last for two full days. If you're off for two weeks, you could be looking at four days of The Dread.
How early The Dread hits you on regular weekends is a reasonably accurate measure of your happiness with your job. Stressful times might see The Dread creeping into Sunday morning, ruining half your weekend. If The Dread makes it to Saturday, it is probably time to consider seeking employment elsewhere.
In spite of how it probably appears, it's Saturday night and The Dread is nowhere near me. Seasoned observers of The Dread and Its Many Manifestations have found that having a wonderful partner sleeping softly next to you is, while not proof against The Dread, then at the very least a pretty strong deterrent.
On an unrelated note, the Flash Fiction Challenge this week is a simple one: Use a random phrase generator to come up with your title and proceed accordingly. My result is fascinating, but I'm not completely sure there's a non-non-fiction story in it: "Sustainable Greediness." I mean, "challenge accepted" and all that, but while it's a fantastic title, it's not quite as inviting as it might look at first glance. I'm not planning on chickening out and re-rolling, but I'm not 100% saying I won't either.