If Jì Jì has appeared in your reading, the book is naming the configuration of completion. Every line of the hexagram is in its correct place — yang in the odd positions, yin in the even ones. This is the only hexagram in the entire book with this perfect alternation. The arrangement is complete. By the book's own logic, completion is also the moment from which everything next begins to come apart.

Classical commentary reads this hexagram as the test of vigilance after arrival. The judgment's structure is unmistakable: 初吉終亂 — the beginning auspicious, the end disorder. The completion is real and the disorder that follows is also real, and both belong to the same configuration. The hexagram appears when the reader has reached, or is reaching, a long-sought completion — and the work is shifting from achievement to maintenance.

What the book counsels is the active anticipation of the disorder that completion attracts. 思患而豫防 — consider the troubles and prepare against them in advance. The water above the fire is a precise arrangement; one knock and it spills, and the fire below changes everything. The reader is being asked to recognise that the period after arrival is the period of greatest exposure, and to attend to the small structural maintenance that keeps the arrangement intact.

Jì Jì's failure mode is the relaxation that follows completion. The book is firm about this. The hexagram appears when the reader has just finished something significant and the temptation is to coast on the achievement. The configuration will not support the coasting. The book's placement of Wèi Jì (Before Completion) as the final hexagram of the entire sequence is the final teaching: completion is never the last word, and the wise stewardship of it knows the next crossing is already approaching.