Your characters, plot, theme, setting, and dialogue are all under your exclusive control. No external force, no magical muse, is taking your hand and making you do anything. That’s why I tend to feel frustration when I see a would-be author blaming one of the aforementioned for hijacking the tale.
You are telling the tale, and should be consciously making use of your novel’s elements to do so. The lion’s share of misplaced blame for novel derailment gets heaped on characters. When you’re saying “My character refuses to do this!” what you’re really telling us is that you’ve failed to give the character proper motivations in the story up to this point, and now your mind does not feel that it would be logical for the character to move on to your desired course.
One method is to go on the new logical route and see where it takes you. If you are a discovery writer, as opposed to someone who outlines, this can be a healthy process. If it’s going to leave your story in shambles instead, or destroy all of the carefully laid plans for your plot, then you need to step back and rewind. Find out where you failed to give your characters proper motivation, and make the necessary changes. Take ownership of your characters as tools to tell your tale.
Talk to them if you want. Do any exercise you need to in order to get to the heart of their motivations. Once you’re done, realize that you’re just using these techniques as a vehicles to communicate with yourself.
The big pitfall of believing your characters are actual, sentient beings is that you lose the ability to tell the best possible story with them. Grow too attached and you’ll always find a way to keep bad things from happening to the character. You’ll enhance their traits until they’re the embodiment of everything you want to be. You’ll give them unrealistic rewards, or become blind to their faults. You’ll stop using them to serve the needs of the story, and they will become a parody of excellence that you may adore, but no one else will want to read.
Sometimes, bad things need to happen to great characters to facilitate the best possible outcome. If you behave as if you’re the characters’ kind and loving creator, instead of an artist who is using a tool to shape your tale, you’re always going to be tempted to mitigate any disasters that occur to your imaginary friends.
Your characters are not people.
They are tools for you to use."