The above is the title of episode 451 of the Incomparable. I had completely forgotten what the episode was about (Captain Marvel), but the expression has stuck with me, connected to something completely unrelated.
A year or so ago, I started trying to really cut down on my phone screen time. It quickly became a sort of competition against myself, leading to all manner of absurd situations where I would hesitate to use the phone even for highly meaningful things. It also made me use any other screens a lot more, and so during normal days the total screen time difference was probably very small. I still think it was good for me though, especially when out and about. I would look up and look around when waiting for something, and I would notice a whole lot just how often other people took a break from interactions by diving into their phones for a few minutes.
I was standing just outside the door to the apartment building where I lived at the time. I guess that I was waiting for someone to let them in or to be let in. The whole situation is probably at least in part a constructed memory. In any case, it occured to me then and there that this was a situation where I would usually take my phone out, I felt relaxed by not doing so this time, and the phrase "my brain unclenched" popped into my mind as a perfect description of the feeling.
Silly progression of events: Using my phone a lot less made lugging a large phone around feel a lot less necessary, and eventually led me to resurrecting - and falling in love with - a first-generation Iphone SE. That, in turn, somehow broke the pattern of restraint and made me use my phone a lot more again. The mind is a weird system.