Write a fic (preferably HP, but the fandom doesn't really matter), based around both versions of the following saying.
First, the rather pessimistic "Only the phoenix arises and does not descend" (in other words - what goes up must come down), and second, the full, slightly more hopeful version: "Only the phoenix rises and does not descend. And everything changes. And nothing is truly lost."
Extra points for actually quoting (or having a character quote) both versions of this "ancient Chinese proverb".
Oh, and just for disclaimerish purposes - for all I know, it may be a real ancient Chinese proverb, but I stole it from The Wake, by Neil Gaiman.