You can do anything - but not everything

Fortune has an interesting article on productivity; here is a highlight.
If you allow too much dross to accumulate in your "10 acres" -- in other words, if you allow too many things that represent undecided, untracked, unmanaged agreements with yourself and with others to gather in your personal space -- that will start to weigh on you. It will dull your effectiveness. You've got to dig into the mess and put those things to rest. Productivity is about completion. 
Isn't it interesting that people feel best about themselves right before they go on vacation? They've cleared up all of their to-do piles, closed up transactions, renewed old promises with themselves. My most basic suggestion is that people should do that more than just once a year. In fact, I tell people to take inventory weekly -- to sort through all of the stuff that they haven't yet acted on. If you can get a clear picture of everything that you have to do, you'll be able to say, "Oh, this is what I have to do right now" -- and then take the next step in getting it done.