point of no return

When I am writing a story, there is always a point when I know that I can no longer turn back. There is an ending and I am falling toward it, like a marble that's been dropped down a series of connected tubes. Procrastination and free will won't deter it, and neither will manipulations of things like plot and character and color of the wallpaper. In some cases, I know what the ending looks like, and sometimes I don't recognize it until it hits me in the face; but once I pass the point of no return (and that's how I think of it... sometimes I hesitate because I know that, somewhere along the way, the story will clasp me to its chest and I will be doomed, but I never know how long a reach it will have), there's nothing that I can do except go onward to the end.
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I am, for some reason, completely obsessed with "All You Need is a Separation Barrier," a short audio documentary by Niall Farrell. And though I'm delighted by the Third Coast International Audio Festival site in general, it being full of treasures and useful inspiration, I keep going back to Farrell's piece and listening to the litany of walls.