[I'm going to start cutting these, because they're getting a bit long, and I rather doubt many of you care about, say, the fact that I brushed my hand against my sweatpants as I pulled it out of position to rub my eye.]
I concluded by thinking that all I'm "supposed" to be doing is observing, but realized that statement is itself a judgement. ;) At this point, I noticed my breath was ragged and my back was hurting a bit.
I shifted around a bit, trying to sit up straight and get my back and legs to feel more comfortable. Then I went back to focusing on my breath. I noticed that my breath was light, but still somewhat ragged. I stayed with the count, but occasionally noticed moments of driftiness here and there.
My left eye started twitching and tearing up for no apparent reason. I chose to uncup my left hand, and slowly reach up to massage it. I lifted my right hand slightly, just enough to pull my left out from underneath it. The back of my left hand (which was cupped, facing upward) brushed against the fabric of my sweatpants as I pulled it out. I lifted it slowly to my face, and first gently wiped away the tears that had built up at the bottom of my eye. I then used it to stretch out the eyelid, first pulling it outward from the side, then up from the eyebrow, and finally rubbing it over my eye in a circular motion. This seemed to quell the twitching. I moved my hand back down and placed it back in position in a similar manner.
I noticed my back was hurting again, so I shifted position slightly and tried to straighten it. Then I noticed the raggedness in my breath had lessened, so I sat with it for a while, counting.
Toward the end of the session, I began to periodically slow-blink, much like a sleepy cat might. [The analogy occurred to me just now as I'm writing -- at the time, I merely noticed the blinking.] I started feeling drifty again, but content. I focused almost entirely on my breath and relaxed, allowing the counting to continue somewhere in the back of my mind.
After what seemed like a short period of time, I reluctantly decided to end the session.