"What would I do with the gaps?"

This is a fear more than a belief, and it isn't always put into words. If you stopped filling every spare moment, you'd have dozens of empty ones a day. It's not obvious what they'd be for. There's a quieter worry underneath, which is what might come up in them.

I'll start with the honest part. Empty moments aren't always pleasant. Two Harvard researchers used a phone app to ask people, at random points in the day, what they were doing, whether their mind was on it, and how they felt. They found people's minds were on something other than what they were doing almost half the time. People were, on average, less happy at those moments than when their minds were on the task. The paper's title says a wandering mind is an unhappy mind. So I won't tell you that an empty gap is a small holiday. Sometimes your mind will drift to the argument with your brother or the state of your savings.

I'd set three things against that.

The first is that the thoughts don't go away when you cover them. The argument with your brother is still there at eleven at night, when the phone goes off and the room goes dark. That's a poor time to meet it for the first time that day. Two minutes of it by the kettle, in daylight, is a cheaper place to have the thought. It's also the kind of moment when "I should just ring him" occurs to a person.

The second is that a drifting mind does useful work that doesn't feel like work. One experiment gave people a creative problem, then a break, then the same problem again. During the break some people did a demanding task, some did an easy task that let their minds wander, and some simply rested. A fourth group had no break. The easy-task group improved most on the problems they'd already seen. The benefit went with how much their minds had wandered. It didn't depend on thinking about the problem directly. That's one lab study, using one kind of puzzle. But it matches the old observation that answers tend to arrive in the shower or on a walk, and rarely at the desk. A gap with a boiling kettle in it is close to the conditions in that experiment. With a phone in it, the gap is more like the demanding task.

The third is my own list of what gaps do, and you can check it against your experience. In a gap you find out how you are. You notice you're thirsty, or your shoulders are up by your ears, or you're more tired than you thought. Tomorrow also gets planned in gaps, without your sitting down to plan it. That's where you remember the form that has to be back by Friday. A gap finishes off the last thing too. The conversation you've just had settles, and you realise what she meant. And you see what's in front of you, which sometimes includes your own children.

None of those happens on demand. They happen when nothing else is happening. A day with no gaps has no room for them, and I think that accounts for some of the feeling chapter 1 described, of a head that feels used without much having been done.

So the answer to "what would I do with the gaps?" is that you wouldn't do anything. A gap doesn't need filling with a better activity. I'd steer you away from resolving to use your spare moments for language apps or breathing exercises. That's the same filling with more worthy material. A person waiting for a kettle doesn't need a project.

If what comes up in the quiet is more than ordinary drift, that's different. If every unfilled moment brings dread, or a low mood settles in, the phone may have been doing a heavier job for you. Chapter 13 says what to do about that, and it's worth doing.