Unfortunately, too many jobs are like mine where you are not afforded the opportunity. "You have to be flexible" or "Priorities change" are all too common of an excuse, yet when productivity drops, heaven forbid you actually bring these ideas to light...
What I would find much more useful would be something like this that tells you how to deal with it when you AREN'T in control of these types of variable. (At home with kids, at work with the boss, when your primary work is with the telephone but you need to do other concentration tasks, etc.)