I can't remove the autobiographical slant from the things I write. You always bring yourself into what you're writing. —Natalie Merchant
Recently, I let my mother read a copy of my latest novel. When she finished, I asked what she thought. "Oh, I loved it!" she said. "It's so fun to see our family in a story!"
The interesting part? I hadn't written about our family. At least, not intentionally.
As writers, we always bring ourselves to our writing. We're like magpies, collecting bits and pieces of our lives and weaving them into a story. Even my fiction is inspired by people, events, and places that are real to me. This is the essence of "writing what you know."
My writing always begins with me, but it doesn't stay there. My characters are often inspired by someone (or more than one person) that I know. And the events might be a bit like the events in my real life, but in my books, I usually try to make them funnier.
Books are also the ideal place for all of the things you "should have said at the time." That's called witty dialogue.
I know writers who often feel self-conscious when they write about parts of their lives. But I think that writing about parts of your life is the best way to truly understand it. Remember that you don't have to publish everything you write. You don't have to share it. You can write it more than once. You can fictionalize it. You can put it in a drawer.
You can reshape it and write a happier ending. It's all up to you.
You can't remove yourself from what you write. It comes from your mind, your heart, and your lived experience. And then it becomes part of that experience.