The Shitty First Draft

Why would anyone want to write a shitty first draft? Why pour hours of hard work into something that you know isn't going to be good enough to share with even your most trusted readers? The answer is simple. When you’re done you have a beginning, middle and end. You've gotten to know each of your characters. You've created their world. You've discovered what’s important to your characters. What they will face. How their actions affect the people around them. You started a journey and made it to the end, a task some writers never accomplish.
I think it’s important to get the first draft written. It creates a foundation you can build on. I've found that by the time I reach the second half of a first draft I've learned so much about my characters that I hadn't know when I began their story. By pushing my way through the first draft I discover little hints that can be woven into the beginning chapters to foreshadow things to come. I know exactly what needs to happen in that chapter I stumbled through.
The revising process is when I look at my work with a critical eye. I add sensory detail that I may have missed. I add in the necklace that is important to my character because it represents the memory of her mother or the brief encounter with a quirky neighbor that explain something that happens later on in the book. And I add the missing details needed to allow readers to draw a picture of each scene in their minds as they read.
Everyone has a process that works for them. Over the years I've discovered that there’s no need for me to stress over what my characters discuss at the breakfast table in chapter two because the answer will come to me as I work my way through the first draft.
How about you? Do you polish each chapter as you write them or do you let the words flow and go back later to do the polishing?