I've been corresponding with Conor Shea of the Daily Kaizen blog recently about the importance of understanding one's own "production" capacity, and how that ties into the lean journey. We've both noticed that managers are terrible at taking the time to really think about what needs to be done -- and what shouldn't be done. As Conor says,

the inability to strategically and systematically stop work is one of our biggest issues, and this of course can trace back to the hundreds of leaders who aren't able to do this as individuals.
I've written before (as has Matt May) about the importance of stopping work. While it's very easy to take on more projects and responsibilities, it's *stopping* work that's critical to getting out of the office and meetings, and into the gemba where the learning happens.

But of course, in order to know what to stop doing, you actually have to understand what you're spending your time on and how much you can realistically accomplish in a day or a week. That's where visual management (and lean tools) comes in. In this case, making managerial work visible enables a leveling of workload, and that means less stress, fewer mistakes, and less waste -- all that mura, muri, and muda stuff.

Conor's group is trying an interesting approach:

We'll lay out the next few days, block out our meetings to leave our available capacity. We'll then create cards with the various tasks that are sized to the estimated length of the task, prioritize in an inventory by due date, and load accordingly. This allows us to match our demand and capacity, and have the necessary conversations (attend meeting? stay longer? etc.) depending on that fit.
Conor and I both think that greater efficiency and reduced waste starts with this deceptively simple question: "How many hours per week do you plan to work?" It's simple in the best sense of the word, in that it leads you down a road that eventually will force you to evaluate production capacity (your time) against production demand (your tasks and projects).

When you answer this question, you can begin to figure out where to put your scarce resources. More importantly, it's the first step in using PDCA to improve the way you work.