Multitasking is not what we think it is. It is not focusing attention on more than one thing at a time. Nobody can do that. When we think we multitask, what we really do is shift our attention quickly between two (or more) things. And every shift is a drain on our ability to shift and delays the moment we manage to get focused again. Trying to multitask fatigues us and decreases our ability to deal with more than one task.