It split into two, and the two scenes were years apart -- all right, I can live with that -- it might be better in that it allows the heroine to grow up some between them -- and the revision is done.
I skip merrily on to the next scene, to give it a minor polish, and realize it's going to need some hack and slash to get into order. And I don't know how much, but it looks major.
All a story's parts have to fit together. The ripple effects from one little scene are very great.