Here is an example summary of this reading selection:

Peter Bregman argues in “How (and Why) to Stop Multitasking” that multitasking (or doing several things at once) decreases our productivity by as much as 40% and that practice reduces one’s ability to multitask. To see what would happen, Bregman decided to unitask for a week. The results were that he was happier, less stressed, more patient with important tasks, and less patient with unimportant ones. He made strides on tasks that required sustained thought, and he didn’t miss multitasking at all. So why, he asks, do we have such trouble unitasking? He thinks it is because of all the distractions in our lives. He recommends disconnecting, giving yourself short deadlines, and reducing meeting time to foster unitasking.

Your summary will differ from this one in the way it is written, but it should include roughly the same information.