Possible Clues:

• That's that
• 'And I don't want to talk about it anymore!'
• "There's no more to say"
• "That's that!"
• 'There's nothing more to say'
• 'We're done'
• 'And that's that'
• ''That's all, folks''
• 'And that's that!'
• Relation's conclusion -- don't argue