“I am at present more impressed with the possible Evil that may arise to You from engaging yourself to him-in word or mind-than with anything else. When I consider how few young Men you have yet seen much of-how capable you are (yes, I do still think you very capable) of being really in love-and how full of temptation the next 6 or 7 years of your Life will probably be-(it is the very period of Life for the strongest attachments to be formed)-I cannot wish you with your present very cool feelings to devote yourself in honour to him.”
letter to her niece Fanny Knight
November 30, 1814 [114]
I think they quoted this nearly directly in Miss Austen Regrets. Olivia Williams as Jane Austen.
A Walk with Jane Austen: A Journey into Adventure, Love, and Faith