My sitting could often be graphed as an upside-down bell curve. Think of the image: at first, I sit down, start focusing on my breath, and my thoughts slowly start to calm down. As my thoughts calm, the curve sinks. Eventually, I get to the bottom of the curve, where I am in a starte of calm, with few thoughts, a feeling of openness, perhaps the "goal" of goal-less sitting.
But then, shortly after, my thoughts begin again, but they are different: usually as they come back up the curve, the thoughts are more like "should I get up now"? "How long has it been?" "Isn't there something I need to do?" Interestingly, I never have these thoughts at the beginning of my sitting, but only after getting into the deepest state of calm.
I guess there's no answer to this, and not even a question (because if I did ask how to make my sitting "better" that wouldn't serve much of a purpose). So I leave this as an observation, and wonder how many of you have the same kind of sitting.