back to the job

i went back to work Monday from being off a whole week and of course i wasn't ready to go back. my reality set in when the alarm went off. in my mind i tried to figure out how i could just get one more day off and promised myself i would rest. that really doesn't work! so, then i convinced myself that when i got home from work, i would go straight to bed. that never happens either, but it seems to help me get moving for the moment. i've been back at work for a couple of days and getting back in the groove. my question to you: why is going back to work after vacation so hard? i feel it's one of the most unholy things to do....of course that's when the alarm is blaring that first morning of return!