with any plant that keeps on springing back to life from its roots, you can do this: Cut back regrowth so frequently that you are draining the roots of their ingredients. This also damages the plant and all that mending takes away from its regrowth vigor. Just turn it into a "fun" thing to do, and know that your new habit is a test of your patience and constancy against that plant's ability to use its stored energy to invest in new chlorophyll. After enough time, the root system will have shrunk (like trees losing leaves) and it'll be easier to kick apart, pry up, and cut pieces out of. One day you'll notice that the regrowth is a lot smaller than it used to be. That will mean you are nearing the end of this plant's life cycle.
David