the.com/watershed moment

The instant before which nothing mattered and after which nothing else does.

means A turning point where events shift decisively in a new direction, after which things can't go back to how they were.

from Borrowed from geography: a 'watershed' is the ridge of high ground that divides river systems, deciding whether a drop of rain flows toward one sea or another. The term moved from maps into metaphor in the 19th century, and 'watershed moment' extended it further — a single instant that works like that ridge, splitting the story of events into a clear before and after.

origin
literally the ridge separating two river drainage systems
metaphor
water cannot flow back uphill, neither can you
misuse alert
overused for mildly notable events, diluting actual significance
recognized
usually only in hindsight, rarely in the moment itself
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