Do you know what's amazing? How I can just write from the seat of my pants and accidentally write something that totally belonged in the story. Like Stephen King said in On Writing, it's like these make-believe characters take over and use me to write their story (I'm paraphrasing).
After finishing my latest scene, I realized that I accidentally fortified my protagonist's character. I wanted to describe her home so I had her walk through it. But why would a character walk through her own home noting all the fine details as if she were seeing it for the first time? And why would she go through the home in the direction she did, when a much shorter path lay straight ahead?
It wasn't until I finished the scene that I realized why the character walked through the house in the manner she did.
Had I not written the scene until I knew why she was going to walk through the house, I think I would have waited for an eternity. Not until I wrote the scene did I understand the character's reason for doing what they did.
It moved the story. It developed the character. It fit. It worked. It belonged.
The tail just wagged the dog.