If you want something done, give it to a busy person.

When you're busy, you don't have time to say, "just one game of candy crush first",

You have to jump from one thing to the next with zero delay.

It's frenetic and stressful, but you also maintain the thread of hyperfocus and activity.

It's way easier to maintain that thread than to start it from scratch.

More tasks can fill in the gaps and help that busy person stay busy and productive.