If the first two stages have gone really well, letting go of the numbers can allow us to develop a deeper and more balanced concentration. However, if we haven’t managed to develop enough calmness in the first two stages, then it’s easy to get lost in the third stage.
This often happens because the counting has been acting as an anchor for our awareness: it stops us from drifting too far away from the breath. So if we let go of the counting we can often float off into distraction.
One way to retain an anchor while letting go of the numbers is to use a physical sensation in the body as an anchor. I sometimes use the physical sensations in my hands in the same way as I use the numbers.
Sometimes at the end of every out-breath I take my awareness to my hands in order to keep me grounded. I use the sensations in my hands much as I’d use the numbers.
The physical anchor is a more refined anchor than the counting because it’s non-verbal — it cuts down on the amount of thinking, so that your mind can develop a deeper level of stillness.
Other times I maintain awareness of my hands throughout the cycle of each in-breath and out-breath. When I breathe in there’s a sensation of rising in the body and so I have a general sense of the gap between the hands and the breath widening. In each out-breath there’s a feeling that the body is sinking, and so I get a sense of the connection between the hands and the breath narrowing. So I notice the connection between the hands and the breath, and this helps keep the mind from wandering off.
Partly I think this works because it makes the practice more interesting. But partly I think it’s something to do with introducing a “stretch” into the practice. What I mean is that I’ve noticed that when my mind stretches to accommodate two separate sensations it seems to calm down very quickly. I can’t explain this, but I offer it as a tool that might be useful.
Other “stretches” involve being aware of the space outside my body while focusing on some inner sensation (like the breath), and being aware of sounds outside of myself while following some inner sensation.
You might want to play around with this idea of creating a stretch in your awareness and see what happens. Just notice two very different and geographically separate sensations, and pay attention to both simultaneously. And notice what the result is.