This ensures that you finish at least the top three tasks everyday. A good start.<p>There is a subset of people who have more than three tasks with equal priority to be done on a daily basis. They will still be overwhelmed, since the carried over tasks over a period of time will be too much to handle for the "role of 3" way.
This is a variant of David Allen's Getting Things Done (GTD) methodology. Instead of three items, he recommends always knowing what the most important task is for any project, and doing that.<p>Definitely worth a look.