"When I get stuck, I move to something else"

It sounds like good management of your time. The report has hit a difficult paragraph and the words won't come. You could sit there staring at it, but it seems more sensible to knock off a few emails and come back to it fresh.

Look at when your switches happen, though. If you kept the tally sheet from chapter 1, try adding a note for a day or two about what was happening in the minute before each one. Some will be outside interruptions, such as a call or a colleague at your shoulder. I'd expect a large share to be yours. And I'd expect those to cluster at particular moments. They come when the sentence won't form, or the figures don't reconcile, or you realise you don't know what you think about section three. This is my observation and I've no study to offer for it. Mark's team did separate interruptions that came from outside from those the workers made themselves, and found both kinds.

Being stuck is unpleasant. You feel a small mental strain, and some doubt about whether you can do it. A notification, or the memory of the expenses form, offers a way out of that strain that looks like work. You leave, the strain stops, and you feel busy and virtuous. It's the same pattern as any habit that removes a bad feeling quickly, and it gets stronger for the same reason.

The trouble is that the stuck point is where the work is. The easy paragraphs of the report would have written themselves. The hard paragraph is hard because it's where you have to decide what you think, and that decision is what the reader needs from you. The stuck point is also where the thread you're holding is most complicated, so leaving then gives you the most expensive restart. You walk away from the most valuable minute of the task, and you've made it costlier to come back. When you do return, you arrive cold at the same hard paragraph, and you're likely to leave it the same way.

There is a version of stepping away that helps, and you can tell the two apart. If you've been working hard at a problem for forty minutes and you're going round in circles, a walk to the kettle can loosen it. The break comes after a sustained effort. You do nothing much during it, and you come straight back. When you switch to escape, it's after ninety seconds of discomfort. You fill your head with another task's rules, and it's an hour before you return.

So when you hit the hard paragraph and feel the pull, stay for five more minutes. Write a bad version of the sentence. Write "what I'm trying to say here is" and finish that. Most stuck points give way within five minutes of actually staying with them, and the pull to leave is strongest just before they do.