Henry James on Unrequited Love

At last there was a silence, and it said so much more than either had said that it scarce needed his fial words. "I've written to you several times."
"Written to me? I've never had your letters."
"I never sent them. I burned them up."
"Ah," laughed Isabel, "it was better that you should do that than I!"
"I thought you wouldn't care for them," he went on with a simplicity that touched her. "It seemed to me that after all I had no right to trouble you with letters."
"I should have been very glad to have news of you. You know how I hoped that - that -" But she stopped; there would be such a flatness in the utterance of her thought.
"I know what you're going to say. You hoped we should always be friends." This formula, as Lord Warburton uttered it, was certainly flat enough; but then he was interested in making it appear so.

[...]

They had gradually stopped and they stood a moment face to face. "Poor Lord Warburton!" she said with a compassion intended to be good for both of them.
"Poor Lord Warburton indeed! But I'll be careful."
"You may be unhappy, but you shall not make me so. That I can't allow."
"If I believed I could make you unhappy I think I should try it."  At this she walked in advance and he also proceeded. "I'll never say a word to displease you."
"Very good. If you do, our friendship's at an end."
"Perhaps some day - after a while - you'll give me leave."
"Give you leave to make me unhappy?"
He hesitated. "To tell you again - " But he checked himself. "I'll keep it down. I'll keep it down always."

The Portrait of a Lady, Chapter XXVII