Memoirs are about memories, but memories can be unreliable. Partly because you were a different person when you experienced them. In the end, you can only tell your story as best you can, but you can talk about that memory from your present point of view.
In Boy, an almost 70 year old Roald Dahl talks about his old school headmaster. He points out that his childhood memories are just that—the point of view of someone who saw the world as a child.