" Every distraction imposes a cost on the depth of your focus. When your brain changes contexts—say, going from painting a picture to answering a text and then back to painting again—there’s a switching cost. Your brain has to load a different set of rules and information into working memory. This “boot up” costs at least a few minutes, and for complex tasks, it can take even longer. The two of us have found it can take a couple of hours of uninterrupted writing before we’re doing our best work; sometimes it even requires several consecutive days before we’re in the zone. "

― , Make Time: How to Focus on What Matters Every Day