Before the Buddha taught that things are inconstant, he had worked at knowing them until they revealed their constancy. Before teaching that things are stressful, he had turned that stress into pleasure and ease. And before teaching that things are not-self, he had turned what is not-self into a self, and so was able to see what is constant and true, lying hidden in what is inconstant, stressful, and not-self.
He then gathered all of these qualities into one. He gathered all that is inconstant, stressful, and not-self into one and the same thing: fabrications (sankhara) viewed in terms of the world — a single class, equal everywhere throughout the world.
As for what's constant, pleasant, and self, this was another class: fabrications viewed in terms of the Dhamma. And then he let go of both classes, without getting caught up on "constant" or "inconstant," "stress" or "ease," "self" or "not-self."
This is why we can say he attained release, purity, and Liberation, for he had no need to latch onto fabrications — whether of the world or of the Dhamma — in any way at all."
Ajahn Lee Dhammadharo
"Keeping the Breath in Mind and Lessons in Samadhi"
For more in-depth dharma articles and instruction, visit: METTA REFUGE