The breath is like a mirror for the mind. When there’s greed, anger, delusion, they’ll show up in the breath. And you find that not only does the breath reflect the mind, but you can use the breath to have a positive effect on the mind as well.
When the breath in the body is full, you find that it’s really resilient and eases your burdens in lots of ways. So experiment to see what a “full breath” is.