I don't know very much about interval training, except that it's effective. It involves short bursts of intense activity interspersed with lower intensity activity.
It's a lot like writing for me. I write in a burst, then I let myself be distracted, then I burst into more words, then I let myself be distracted. Over and over. It's part of the process. If I stay in flow, I write more but I don't write better. In flow, the writing becomes like trance and trance logic doesn't play well in writing. I read an article on storytelling this week. It discusses James Joyce and Finnegan's Wake this week that points out no one can actually read hundreds of pages of trance logic.
You might not think that trance logic is a problem for you. You might think that you are sharp and logical and a brilliant negotiator. In Willful Blindness Margaret Heffernan explores many situations in which smart people do dumb things because they are so tired or so much in flow that they enter a world of trance-like thinking, a world that has much in common with the certainty we feel in our dreams.
Daydreams are not like night dreams. They are not intense and gripping and they do not make us feel certain. They might not make us feel good, either. But maybe the point of daydreams is not to engage in a quick delusion of happiness. Maybe daydreams create a distraction from intensity so that what we return to is smarter, sharper, more precise.
Rest is not happiness. But without rest, happiness is not possible for long.