Diary or Memoir
In every other nonfiction genre, you're writing to an audience — or at least so you hope. But when you sit down to write about your life, you have to decide whether it is primarily for you that you're writing or whether you want to reach out to others.
If it's the former, you are making entries into a diary or as some might say, “journaling.” If it's the latter, you're writing a memoir. This is the final issue you must resolve before you begin writing.
An example of this distinction is two prominent accounts of living under Hitler's specter and the shadow of the Holocaust. Perhaps because of its straightforward, impassive chronicle about life as an assimilated Jew married to a gentile woman, I Will Bear Witness, A Diary of the Nazi Years by historian Victor Klemperer is extremely effective in portraying the day-by-day deterioration of life under the Nazis. But so far as the writing goes, it is a diary:
“New Year's Eve '39, Sunday evening. This Christmas and New Year's Eve we are decidedly worse off than last year, we are threatened with the confiscation of the house — despite that I feel better than I did then…. I am now convinced that National Socialism will collapse in the coming year. Perhaps we shall perish with it — but it will certainly end, and with it, one way or another, the terror.”
Whether a work is a memoir or diary is not determined by the format but rather by conforming to the guidelines of writing nonfiction, in which case it's more likely a memoir. Another difference is that memoirs are written keeping the reader in mind by eliminating facts and events that would be of no interest to a stranger.
Probably the most famous “diary” to emerge from that era is The Diary of a Young Girl by Anne Frank. Originally, Anne set out to compose a diary written strictly for herself, but at some point she decided that after the war she would publish a book based on her diary. Consequently, she rewrote and edited what she had previously written, keeping the reader in mind by deleting what was not of interest to others and making the text more readable. She continued in this style, writing her entries to her imagined reader, Kitty. Consider how personal and universal the following passage is and how easygoing the tone.
Tuesday, March 7, 1944
“Oh, I haven't forgotten how to laugh or toss off a remark … and I can still flirt and be amusing, if I want to be….
“But there's the catch. I'd like to live that seemingly carefree and happy life for an evening, a few days, a week. At the end of that week I'd be exhausted, and would be grateful to the first person to talk to me about something meaningful. I want friends, not admirers…. The circle around me would be much smaller, but what does that matter, as long as they're sincere?”