The joy, the gratitude, the exquisite delight of her sensations may be imagined. The sole grievance and alloy thus removed in the prospect of Harriet’s welfare, she was really in danger of becoming too happy for security. – What had she to wish for? Nothing, but to grow more worthy of him, whose intentions and judgment had been ever so superior to her own. Nothing, but that the lessons of her past folly might teach her humility and circumspection in future.
– Jane Austen
Emma, Chapter 54. After Mr. Knightley delivers the news that Harriet has accepted a second marriage proposal from Robert Martin, Emma is elated. Acknowledging her past foolishness, she promises to be more humble and circumspect in the future. And she hopes to grow more worthy of Mr. Knightley, whom she credits with superior judgment to hers. She uses the word “alloy” as a metaphor for her past matchmaking misperceptions that could have ruined Harriet’s well-being and happiness. This shows how much Emma has matured and seen the error of her ways.