So you think you don't have enough memories to write your life story? You are wrong. They just need to be brought out to the here and now. There is an excellent way to do it, take notes. It will take time, but you will see results.
There is nothing to stop you from writing your memories down on a note pad or in an exercise book. But memories rarely arrive in chronological order and when you start writing your book of life stories, you will be forever flicking backwards and forwards through the pages trying to find the note that you want.