Pruning From The Inside.

To maintain trees at a certain size
For it to maintain "that quality" of a tree
It has to be pruned from the inside
Following more of a methodical process 
That moves in an understanding of growth.
But first
In what may take a couple years -
An architecture of branches must be created.
​Then one can return on intervals
And make cuts repeatedly
In method.
Part of the architecture is about
creating a structure that can be returned to again and again
and easily reduced to its managed form.

One's cuts are much lower than if you were approaching from outside the crown.
From here growth sprouts and grows.

You can't teach pruning.
There are some principles -
You must know how growth and buds form in reaction to cuts -

It is a poetic.