Daydreaming and singing to yourself is not entertaining. It's just something that an unstimulated brain does. To get to that destimulated place is the object imo - where what you're doing is so habitual that every step seems like a breath, and you only notice the ones you miss.

I remember before I learned the basics of cooking how hard everything was, and how much I had to concentrate. These days I'll spend 20 minutes cooking something, plate it and go to the bathroom, and have forgotten what I cooked before seeing it again. I remember when I was learning Spanish, and every successful paragraph I read merited a celebration, and now I sometimes can't remember whether something I read was in Spanish or English an hour after I've read it.

My biggest improvement in writing came after I stopped listening to music while doing it. Get it over with, then listen to music. Once you get into the habit, it's like taking a nap not having a party. I remember a factory I worked at in my 20s where I got up to doing 76 hour weeks with no days off because I was so good at what I was doing, I entered a timeless place. There was no time to get bored in. I'm sure I might have hummed, but I wouldn't remember. I certainly wasn't thinking about anything important; those machines could have ripped my hands off.