When I asked Alice Sebold about whether or not writing Lucky (her memoir about her brutal rape) was cathartic, she said no--that she had worked through those feelings before writing the book. She said, "I had already done my personal work. Memoirs should serve the people reading them, not the author writing."
Consider that comment in contrast to Robert Frost's famous insight about writing and feeling: "No tears in the writer, no tears in the reader. No surprise in the writer, no surprise in the reader."
I've been writing poetry and memoir for the past two years about my parents' illnesses and my father's death. Feeling is essential to me while I write. So is discovery. I can never claim I've worked out my feelings and thoughts in advance of writing--be that memoir, poetry or fiction. (That doesn't mean I write only to serve myself; I almost always imagine myself speaking to others as I write.)
Poet Ellen Bass addresses this as well in a recent online Poets & Writers intervew. I like how she says that her writing comes from something she's "trying to work out." To me, if I already have the thing settled, there's no reason to write about it.
Here's what Ellen says:
P&W: How did your mother’s death affect your writing?
Ellen Bass: Writing poetry for me was one of the primary ways that I grieved. I found that working with the poems was more natural to me than any other outward rituals or ceremonies around her death. I just thought during that whole period how fortunate I was to be a poet. I don’t know what people do who don’t have a way to sit with their experience in a tangible way. . . . Very often a poem comes from something that I’m trying to work out in my own life. Often I’ll write the same poem many times if there's an idea I’m grappling with. I’ll write it over and over in poems that don’t ultimately succeed until finally I have some entry into the poem.