Coming back to work after a vacation can be, ironically, pretty stressful. There is a mountain of backlogged tasks you must tackle before even getting to the current projects demanding your attention. Even the bite-at-a-time method can seem daunting.
Instead of the load all coming down at once your first day back, I'm in favor of using your last half-day of vacation as a re-entry period. Yes, you're technically still on vacation, but to help that relaxation you've been experiencing carry over into the work week, spend some time catching up.
Like the night before the first day of a school year, you get your backpack ready to go, lay out your clothes for the following morning, and you double check your class schedule (or triple check it for you achievers). Spend the final hours of vacation to tie loose ends and answer as many emails before work as possible. It will be worth it.