To avoid being hurt by thorns and brambles, we might consider covering all the mountains with leather. That would be impossible, but putting on shoes would serve the same purpose.
Similarly, if we tried to subdue all our outer enemies, we would never succeed.
Once one was eliminated, another would rise against us.
While doing this, our anger would continue to breed new foes.
The only way to overcome our enemies is to turn inward and kill the real one, which is our own hatred.