"I believe that true identity is found . . . in creative activity springing from within. It is found, paradoxically, when one loses oneself." - Anne Morrow Lindbergh
I believe this is true about all writing—fiction and nonfiction. The act of writing opens a channel to the page from an inner world that we tend to keep under tight control lest some 'inappropriate' idea escape. If you really relax and let it flow, i.e. 'lose oneself', often the words that find their way to the page surprise and inform. And once out there, we can realize even the 'inappropriate' ideas have value, an honesty that will resonate with others far better than any carefully shepherded words are able to.
When you sit down to freewrite, do so with the intention of staying out of your own way, of not directing your thoughts into safe, 'acceptable' channels.
"Out beyond ideas of wrongdoing and rightdoing, there is a field. I'll meet you there." - Rumi