Day 2. I daren't call it meditation, since I've no idea what I'm doing. Instead I call it my "sitting quietly practice". 10 minutes again this morning and it was pretty much the same as before, in that I wasn't very good at it, but the ways I wasn't very good were slightly different.
When I started, I immediately quietened down to a level that took me a few minutes yesterday. That was a surprise. The experience of focusing on my breathing was considerably more vivid too. I could really lose myself in the sensation of the breath at the tip of my nose (thanks Rob A for passing along this advice). It sounds odd when I try to describe the difference: It's like I was only focusing on the concept of breathing yesterday, but this time I was having the physical feeling of it, located on my body, in my nose.
Speaking of sensations... I also noticed that my continual "let it go" response (for when I notice my attention wavering to sudden noises, vision, or my aching legs) was itself a thing occupying me. A better response was to let the sensations pass through me and go away of their own accord. That felt like a better way to be quiet than keeping busy, furiously pushing things away.
A new distraction was that I was watching myself too much. It happened as soon as I found a new way to behave. This isn't going to make much sense: It's like there were two "me"s. One was doing the breathing and the quietness, and the other was churning away with thoughts just as much as any hour of the day, only saying things like "oh, that's good, good breathing there". (And I guess I don't literally mean two "me"s. Just that I - my thoughts - moved smoothly from doing something, to considering myself doing that thing.) That kind of introspection isn't terrible, but I'd ideally do it from here - the other end of the day - than in the moment itself.
Other than that, the time seemed to go a little quicker, and I occasionally had the familiar sense of frustration and being trapped, though not to the same extent.