Another reason people think they cannot work in small pieces of time is that they do not see research as something you can relax with in a casual way. I used to do it in a relaxed way, most of the time, but then later I started to do it as relaxation. It was the activity in which I was most interested (except for things like being at the beach, of course) and where it was easiest to just be myself.
I lost those associations later, lost possession of my research, really — that is the way to describe it, it is though it had been an organ that got cut out and nailed to the wall, someone else’s trophy, perhaps. But the point remains that if you see research as relaxing, then you can do it in small pieces and when you are not at your best, even.
Key in all of that, though, is that your research has to be yours, your work that you have and feel you have a right to have. Not merely a thing that proves something about you and that is external to you, but something that is a part of you, something that you do, simply, do simply and simply do.
Then it can be something you relax into and, as I keep saying, you can do it in small pieces of time and even when you are at much less than your best.
This, I think, is kept secret because people want to prove, or have to prove tiresomely that what they are doing is work. My suggestion is that the emphasis on difficulty and work-ness of research, although seen as a necessary defense of said activity, may be too costly since it is so discouraging.
Instead one could say yes, I am playing instead of entertaining you or helping you with your work. I may indeed fail to create a marketable product. Still, I will have fulfilled my contract at least to some degree by trying, since by this play I remain informed. And precisely because it is play, it improves teaching, so there (you dour and ugly fools).
It is also not true that “the only good book is a finished book” or, in other words, that the only reason to finish your book is to put it on your vita. The reason to finish things is to figure them out.