This is an incantation to be anchored to the arising of anger.
The purpose of the incantation is train the mind to
1: discard that which is unskillful and
2: retain that which is skillful
by transforming the anger into discernment.
Why it works …
This, I believe, is precisely the purpose of the 2nd “fold” of the Buddha’s 8-fold path to the end of suffering: “Right intention”.
It is also my strong intuition that the more evolved “faculty of discernment” evolved “on top of” the less evolved “faculty of aversion”.
i.e. The “push away” primitive is leveraged and repurposed to “push apart” an idea into its component parts.
Specifically, an idea within our predictive model of the world which we have “mixed feelings” about.
We use the faculty of discernment to resolve those mixed feelings by pushing apart the idea into “that which is unskillful” and “that which is skillful”.
Thereupon we may discard that which is unskillful while seeking to re-integrate “that which is skillful” into our predictive model in a fashion that more accurately explains our experiences and thus is of superior predictive power.
Therefore training the mind to transform anger into discernment is not only skillful, but natural.