" Unfortunately, that’s often not the case: We must wait for tasks or information or other things to be completed before we can move on to the next step. And so we multitask, but not on the task level—we multitask only on the project level. While one project is on hold for an hour or a day or a few days, we can be working on another. I’ve found that three projects works best for this type of project-level multitasking—any more than three, and you begin to lose effectiveness. "

― Leo Babauta , The Power Of Less: The Fine Art of Limiting Yourself to the Essential