Writing is like that. We sit down in front of a computer and imagine words that we might not say out loud in real life. We imagine people in situations that are made up of whole cloth, saying words that we pluck out of the air, and keep on doing that until we've filled our allotment of pages for the day. And when it comes time to send our manuscript forth into the world, we "put on our game face." However, instead of facing people for a limited amount of time, we're going to put our words out there for thousands (we hope) to read and comment on for as long as the book is in print.
Some people like to use a critique group for the exchange of ideas. Others prefer to do it solo. As one author of my acquaintance says, "No one reads a single word I've written until the manuscript is sent to my editor." Whichever way a writer prefers to do it--whether with others contributing ideas and reacting to what's written or by never sharing the manuscript until it's completed--ultimately the responsibility for what's going down on that paper is the sole responsibility of the author. And that's a scary thought.
I love the quotation that I sometimes use as a signature line. "Some people hear voices when no one's around. They are called mad, and sit in a room all day and stare at the walls. Others are called writers, and they do pretty much the same thing." I may not have the words exactly the way writer Meg Chittenden said them, but writers will know what I mean--and nod. How about you?