Grief, lamentation, pain, affliction, and despair are suffering. To be united with what is unloved or to be separated from what is loved is suffering. Not to obtain what is longed for is suffering. In short, life is suffering. This is so because life is impermanent and filled with constant change.
Death puts a final limit on everything.
This is indeed the stark reality of the human condition. In this way they pile up countless debts, and some day they are going to have to honour those debts. But a disciple sees things quite differently. We are hemmed in and limited, trodden underfoot, tormented and abused in every way. If we close our eyes to this truth, we do so to our own detriment.