I've become very good, over the years, at two things in particular: creating the space for myself to do deep, focused work on one thing intensely for a span, and batching/circumventing/streamlining smaller tasks. Alongside this, I've done a lot of work on cutting down on lots of 'time sink' activities like social media, Twitter being the lingering exception (though even that in phase).
I don't bring this up out of a sense of smug superiority, but because one thing that's left me with is a strange difficulty in spending small units of time. If I have an hour, I can get a hell of a lot done (and have probably planned in advance what that is going to be). If I have a bunch of smaller tasks on my plate, I can spend thirty minutes cracking through a bunch of them all at once, and otherwise, they can sit there until their time comes round again.
There are many reasons why this works for me (a lot of it I think comes down to activation energy and spending it as tactically as possible). The problem is, if I have ten minutes, I often have no idea what to do with it, or even lack the capacity to spend it happily doing nothing. My brain will be rifling through the things it might do and rejecting them due to 'not enough time' or 'too much risk of absorption. It's that muddy middle where to actually spend that time well would mess with where my brain is focusing and make it hard to move on.
To sharpen that last point slightly: I fear either starting-but-not-finishing a task and thus having another open loop to juggle in my head (see the Zeigarnik Effect), or getting so into it that I don't effectively break away, leaving me with a kind of cognitive inertia that tails me into whatever activity put the upper limit on that time.
'Doing substantially nothing' is an entirely fine way to spend ten minutes, and I am not very good at it. Once more, this isn't out a misplaced boasting around productivity and unidleness -- I consider this a kind of small liability, really, an unfortunate byproduct of other habits and systems that are actually good.