This comment brings many ideas to my mind.
One breath at a time does sound meditative, but meditation is action.
One breath at a time is one hevel at a time, one moment at a time.
I am trying to suggest that the Halakhic approach does not seek to do everything all at once, but examines life in action in bite-sized pieces. Every moment is important and worthy of consideration.
One is that yes, meditation is action, but it is also concentrated thought (such as Tibetan Buddhist analytical meditations) and this makes me think of talmudic study, which is clearly concentrated thought.
And yes, I couldn't agree more that "Every moment is important and worthy of consideration," which is something the halakhah certainly instills in a way that I think is different from the very popular and perhaps effective motto to "be in the now" or "be in the moment."
While these sayings are certainly worthwhile, I think they lend themselves too easily to simple inwardness and attention, if that. While the halakhah asks one to focus on the moment, by asking one to follow the commandments of Hashem, these I see as very different responses to life.
In some ways, the popular mottos could be seen as a "minimalist" view of life -- be attentive to anything that occurs. Which again is in drastic contrast to Rav Rosensweig's insistance of encouraging a "maximalist man of destiny" from his essay "The Spiritual Legacy of Noah and Avraham" or a "maximalist halachic lifestyle" from his essay "Chanukah as a Holiday of Idealism and Maximalism."
One of the things that attracts me to the Modern Orthodox tradition is this emphasis on a maximalist viewpoint, because I believe that Hashem deserves nothing less.