The first link: lead out the full text, lay the emotional tone of xx, render the atmosphere of xx, compare the emotions of the characters and the location of roll call time, explain the emotions, and pave the way for lyricism or scenery writing below.
Intermediate sentence: connecting the preceding with the following, transition
End couplet: Summarize the whole poem, deepen the theme, and take care of the first part, which makes people memorable.