I should mention that although the one-pointedness I experience in the location of my awareness occurs as a necessity of breath, there is a feeling of well-being.
There’s a description in the Pali Canon of two “cessations” that I think summarize how a feeling of well-being can arise in connection with a necessity of breath: they are, “the cessation of ease apart from equanimity”, and “the cessation of happiness apart from equanimity” (Sanyutta Nikaya volume V 215).
The equanimity referred to is defined as equanimity with respect to the multiplicity of the senses (Majjhima Nikaya 220), and the necessity that I feel in the movement of breath turns out to be exactly the need for equanimity with respect to all of my senses (with no sense left out) in order to feel ease, and in order to be happy.
As I have said, for me at this time, a feeling of necessity in the movement of breath seems to speak to my need to include equalibrioception, proprioception, and graviception in my awareness (whoa, checking online for a good description of graviception just now, I discover an article about graviceptors other than the otoliths–news to me!).
In addition, I think there is a “suffocation response” panic that makes relaxation and calm a part of the practice that occurs in response to feeling such a necessity of breath (you can read more about the “suffocation response” here).
I would say that the inclusion of all the senses in awareness can make the whole experience of a necessity of breath a part of well-being, and draw a person through the suffocation response.