Harper's experience greatly changed his life. He was sitting at the breakfast table and talking with his dad about something he had just read in the LDS Church News. He remembers he was eating cold cereal, but he can't tell you what cereal. He remembers sitting to the left of his dad, but he can't remember the clothes he or his dad were wearing. Some details are fuzzy, yet he can remember exact words his father said. Word for word. The experience was significant -- and, he says, he was sacred.
Joseph Smith's recollection of his First Vision experience in the Sacred Grove has many of the same features as Harper's recollection. Some details Joseph remembered were vivid and concrete. Other details were uncertain.