The twentieth zone rests on what repeats. Family customs, dates of one's own, the familiar order of things — whatever happens the same way every year and is dependable for that reason.
What separates it from arcanum six is reach: arcanum six needs the close circle, while the twentieth needs a line running backwards. Ancestors matter to it, and continuity, and what was there before it and will remain after it.
The loss of a tradition is lived through by this zone more heavily than the loss of comfort. A custom called off, a circle that has broken up, a habit interrupted — all of that knocks the footing away.
In practice: it is worth setting up customs of one's own deliberately and keeping to them. For the twentieth zone that is not sentimentality but a way of standing on its feet.