The three characteristics of impermanence, dissatisfactoriness, and no-self are so central to the Buddha’s teachings that it is almost inconceivable how little attention the majority of “insight” meditators give them. I cannot possibly overstate the usefulness of trying again and again to really discern these three qualities of all experience. They are the stuff from which ultimate insight at all stages comes, pure and simple. Every single time I say, “Understand the true nature of things,” what I mean is, “Directly perceive the three characteristics.” To perceive them thoroughly and directly is to be awakened.
Daniel Ingraham – “Mastering Core Teachings of the Buddha”