When was the last time you really took a sustained break from work? No emails. No calls. No taking care of that one little thing. For most of us — particularly in the United States -- it's been too long. As we head into the end-of-year holidays, we asked University of Texas psychology professor Art Markman and Cornell University associate professor Kaitlin Wooley to explain why it's so important to take real vacations (or even staycations) and how individuals, bosses, and organizations can do a better job of making them happen.