From that moment I observed my friend’s behavior attentively; and I could then perceive that his partiality for Miss Bennet was beyond what I had ever witnessed in him. Your sister I also watched. Her look and manners were open, cheerful, and engaging as ever, but without any symptom of peculiar regard; and I remained convinced from the evening’s scrutiny, that though she received his attentions with pleasure, she did not invite them by participation of sentiment. If you have not been mistaken here, I must have been in an error. Your superior knowledge of your sister must make the latter probable. If it be so, if I have been misled by such error to inflict pain on her, your resentment has not been unreasonable. But I shall not scruple to assert that the serenity of your sister’s countenance and air was such as might have given the most acute observer a conviction that, however amiable her temper, her heart was not likely to be easily touched. That I was desirous of believing her indifferent is certain; but I will venture to say that my investigations and decisions are not usually influenced by my hopes or fears. I did not believe her to be indifferent because I wished it; I believed it on impartial conviction, as truly as I wished it in reason.

– Jane Austen

Pride and Prejudice, Chapter 35. Darcy in his letter to Elizabeth explains his part in the breakup of Jane and his friend Charles Bingley. He states that he believed Jane did not love Bingley – he interpreted Jane’s reserve as indifference as a lack of love. He now admits that his first impressions of Jane were mistaken.