You may not feel like coming out of your office on monday. Not because you don't feel like being around your coworkers, but because you have an intense amount of work to get done, and the only way you can see yourself taking care of it is by limiting your contact with the outside world. Fair enough. Make sure everyone knows you're buckling down for the sake of work and not just avoiding them. Ironically, by the time you're in the mood to chat midweek, everyone else is going to be in aloof mode. At the end of the week, once your desk is clear, you'll get to sit around with your feet up.