Every voice matters - in memoir writing I believe we have each lived important lives. Oh. Maybe not headline important (although I have had many in my classes making headlines). You matter to yourself, to your family and friends. Never doubt that the universal and particular things you have experienced matter to a larger audience because they do. Somewhere someone will read your book and say - wow! I didn't know anyone else went through that sort of thing and survived it ok. You can give hope and power to people you don't even know.
We are a storytelling world. From earliest life on this planet, people evolved telling stories. I imagine the first stories were about where to find food or shelter, how to avoid predators or danger, who were friends to be trusted and who were not. How families are created, how illness is helped - or not, how to handle those just born and those who died.
Guess what? Those are the same sort of stories we tell today: how we deal with life's joys, successes, failures, problems, life and death - but in the contemporary parlance of this digital age. Our lives, our stories do matter.
First draft writing is always meant to just get it down - the entire manuscript. If it is creative writing you can go through a number of edits to smooth out errors, remove unnecessary scenes or change characters or conflict so all of it seamlessly fits together. In memoir writing it is the same thing - just writing it all down then worry about which scenes stay and which scenes you can leave out. But keep on writing - doubting yourself is a waste of time - if you want to write - you are a writer. Remember that.