Every moment is dukkha, unsatisfactoriness. Why? Because in every moment, we can be doing something or not doing anything. In that action or non-action, there is either presence or absence of greed, hatred, and delusion—the three poisons. These three poisons can exist in gross, subtle, and extremely subtle forms. Only a fully enlightened being is fully free from them. All of us are not. Those of us, a minority, who are practicing for enlightenment are also not free from them. Greed, hatred, and delusion suffuse all of our doings and non-doings in every moment for all of us.
Thus, in every moment, whether we are doing something or not (non-action is also a form of action), we are caught in the three poisons with reverberations throughout the net of Indra—the vast interpenetrating, inter-existing network of sentient and non-sentient beings in the cosmos. There is no escape. Every thought, word, deed in every moment inter-is with everything else in the universe. Thus, interbeing.
We fall short. And as long as we are not enlightened, we fall short. This also begs the question of how anyone from their own side can actually free themselves from these poisons and the dukkha they cause. It is by definition impossible. How does perfection come from imperfection? It is not possible.
But what about buddha-nature? Impermanence is buddha-nature, is it not? Yes, change is a fact. But there is no guarantee that change will inevitably be for the better. Besides, how and where and when was buddha-nature ever possible in the first place in beings caught in beginningless suffering and confusion?
In short, we fall short. We can know and see this as an existential reality, not just as an idea. This is hamartia or sin, at least in one sense. Not something our ego or pride likes to hear, but it is the simple naked truth. As sinners, we sin. Period.
How then? We are in dire need of grace. For without grace, there is no true, lasting, complete freedom from poisonous defilement and dukkha. In fact, our longing for practice; our ability to practice and awaken and transform; our enlightenment itself are all rooted in grace. No grace, no enlightenment. Something to reflect upon deeply.