The number of breaths we will take in our lifetime isn't set until we die, but each breath we take does reduce the number remaining from that eventual total by one, amirite?

You should look into Hitsuzen and Guzen. They are two competing philosophies from Japanese Shinto. Hitsuzen is "the inevitable" and Guzen is "the happenstance". While one side would say each breath was inevitable the other would say each breath was already your last until you breathed again.