I was recently revisiting Mark Forster's concept of the "closed list." (Mark is the author of Do It Tomorrow, and a leading productivity consultant and thinker based in the UK who's well-worth reading.) The closed list is essentially a to-do list that's limited by the amount of work time you have available during the day. Mark's argument is that making a daily to-do list containing 14 hours of work is pointless, not to mention frustrating and self-defeating. If you're only working 10 hours a day, you'll never finish all the items on your list no matter how efficient and motivated you are. So why bother putting all those items on your list for the day? You'll have to move it to another day.
Instead he advocates a to-do list that can be completed within your workday -- and that includes accounting for the unexpected problems that inevitably derail your schedule. It's a reality-based to-do list.
The closed list reminds me of the brilliant simplicity of the kanban in a lean production line. For those who don't know, a kanban is a signaling device (usually a simple card) that controls the amount of work-in-process inventory. When a person on a production line finishes his operation (grinding a piece of metal, say, or checking the credit scores on a mortgage application), he sends a kanban to the previous station. This signals that he's ready for the next piece of metal or the next mortgage application, and the upstream person then sends the next item down the line. For the purpose of this blog post, what's important is that the kanban controls the amount of work-in-process inventory: there can never be more inventory than there are kanban cards, so you never run into Lucy's famous problem of too many chocolates coming too fast down the assembly line.
Mark's closed list -- which is really the father of my principle of "living in the calendar" -- has the same benefit of the kanban in controlling the amount of work-in-process inventory. It prevents you from taking on more than you can handle in any one day, and thereby forces you to prioritize. You can't do more than 8, or 10, or 14 hours worth of work -- you have to decide what's most important, and ruthlessly weed out the rest (a la Jim Collins' stop doing list). It also creates a basis for a conversation with your boss when yet another "critical project" with an impossible deadline is added to your load.
The closed list doesn't reduce the amount of work you have to do. The truth is, that work is pretty much infinite. But it does force you to assess your work more closely, and helps you prioritize and keep you focused on what's really important to you.