An autobiography is a story that records part of your life, usually the bigger events that would give interest to others so when writing an autobiography, it’s better to have as much information as possible. You want the reader to find themself in your shoes, and giving lots of specified information can help achieve that.
A big problem people complain about is the fact that we always forget the details. We only remember the event: “This happened”, “That happened”, “We had fun” But never the small details like: “The sky was a clear blue”, “The building was tall and had several windows”, “There were many cars in the parking lot”.
One way, to preserve those specific features, is to write on it while the memory is still fresh. Keeping a journal with you is best so you can record the notes you will want to use while you write your autobiography. That way you can look back if you need the info and there you’ll have a more specific paragraph or page of something that may have happened a long time ago!