One of the most important ideas in this book is how to reduce stress by eliminating “open loops”. Most people keep a “todo list” in their heads. This list has everything from taking your vitamin to refinancing your house. David Allen calls these “todos” open loops. Your mind keeps churning all of these open loops all  the time so that it can bring them up to you as needed. Unfortunately, the “as needed” is often at times when you can not take action… Like when you’re in the shower and that “pick up milk on the way home” todo pops into your head. These open loops tend to keep you from focusing on the task at hand and therefore, cause stress, and make you less effective.

This is just one example. Getting Things Done presents an entire system of dealing with things, closing the open loops and handling the “todos” more efficiently. There are many ideas, many of which will strike you as “a blinding flash of the obvious”. Simple ideas, that together, make up the GTD system.