"Once upon a time, a few mistakes ___ ..." (Taylor Swift lyric)

AGO

Think of a word that pairs with "long" to describe something in the distant past, often used in fairy tale openings.

This clue references a line from Taylor Swift’s song "All Too Well," where she sings, "Once upon a time, a few mistakes ago." The word "ago" fits perfectly as the missing piece, completing the lyric’s nostalgic tone. The phrasing plays on the idea of looking back at past errors, making "ago" the natural choice for the blank. If you know the song, the answer clicks right into place.