People who brag about being able to multitask are liars, says Harris. Because every time you're multitasking, "it's another way of saying you're doing many things poorly." Not so impressive. From Harris' Big Think talk:
Multitasking is a computer derived term. Computers have many processors. We have only one processor. We literally neurologically cannot do more than one thing at a time.
Harris' comments are supported by a growing amount of research on multitasking that suggests multitasking can actually be less efficient and can also cause stress (no big surprise there).
If you're looking for an antidote to multitasking, it could be as simple as focusing your energy on one thing at a time. One great way to practice that is by trying mindfulness meditation—a topic which Harris has devoted a book to called 10% Happier.