The extended meaning is not to dwell on the past, but to grasp the present and face the future. The "preface" is written in front of the article, not the text, nor is it an important part of the article. The past not only represents loss, but also includes gain. Whether it's gain or loss, good or bad, it's all over. The original sentence is "everything in the past is a preface." From the beginning of Shakespeare's play The Tempest, it is one of Shakespeare's famous words.