This may, of course, mean rethinking a lot of ideas that you felt were concrete. It may mean ditching the research you did into 1890s fashion and music. But although you lose those ideas, you gain new ones. Playing with ideas is much the same as children playing with building blocks.
You may cry for a moment when your masterpiece is destroyed, but you move right on to building a new one. The trick is not to fall so deeply in love with any idea that you can’t contemplate tearing it apart and putting it back together again. Yes, it will be painful. But what you come up with may be better. The writer’s job is not just to write; it’s also to rewrite and rethink and revamp. There are millions of ideas and thousands of words to choose from, and no single one of them is the only perfect option.
The late Sidney Sheldon once said that no author should ever know how the book was going to end. Some writers work that way. They allow the plot to meander like a river until they feel it has reached its goal. They believe that knowing too much about what is going to happen can ruin their creativity and make the book flat.