Productivity guru Gina Trapani calls this "running a morning dash." When she sits down to work in the morning, before she checks any email, she spends an hour on the most important thing on her to-do list. This is a great idea because even if you can't get the whole thing done in an hour, you'll be much more likely to go back to it once you've gotten it started. She points out that this dash works best if you organize the night before so when you sit down to work you already know what your most important task of the day is.