Robert Frost wrote about The Road Not Taken, and I think about that a lot as I write. I made a choice this week to have one of my secondary characters, Barbara, step into a situation that revealed more about her, and in the process, it revealed a bit more about Anna, my MC. I had intended for Barbara to veer into something different, but she didn't want to go there. She wanted the road NOT taken.
Come on, you fiction writers, you know exactly what I mean. You create a character, and non-writers think you "make" them go where you want them. But once a character has been defined to a certain degree, and she begins to "live" for you. Like the Velveteen Rabbit she becomes "real" and then look out! Characters do lead writers along. As Stephen King says in "On Writing," you uncover the bones of your story--and your characters are the ones who do the real work for you. So make them strong and give them a variety of tools for their job--physicality, personality, spirit, and all the other strengths and weaknesses that make them resonate with your readers, then let the story unfold!