Personal historians are often asked how people should organize a life story. Should they do it chronologically, from birth onward, or should they highlight various themes in their lives. Or should they pick certain important or influentual events?
Any of these are fine. It depends on what they want to tell. Some people like the traditional "I was born" format - or as Dickens put it with the fictional but possibly autobiographical David Copperfield "I am born." Others have particular parts of their lives, say an event or a meeting that led to an important decision.
Stream of consciousness might even work for some. Mark Twain's autobiography, as published so far, jumps about with what seems like no particular plan. He covers many pages describing a house his family rented in Italy, generally fewer on the critical issues and leaders of his day. There is little to nothing on his early career.
There is no formal pattern to personal histories or memoirs. The important thing is to tell the story. And personal historians can help do that.