Possible Clues:

• Mr. Hyde, to Dr. Jekyll
• Classic breakup line ... and phonetically, a correction needed to understand the starred clues
• Classic breakup line
• Blame-shifting breakup line ... or a homophonic hint to 20-, 34- and 41-Across
• Fault line
• Third cliché of the speech
• Classic breakup line, and a hint to the formation of this puzzle's theme answers
• Breakup line from a grammarian?
• Narcissist's breakup line?