I reached the stage of a (non-fiction) writing project where I had tons of notes, but no sense of what an eventual manuscript might look like. I discovered Zettelkasten and it was a revelation, not because I think it's the only way to write, but because it was an answer to my precise problem of how to turn a ton of notes into a manuscript. I'm still a long way from being finished with my project, but I can get my pen moving every day and that in itself has been an enormous relief.