It meant that Diana had not waited for any explanation, however halting and imperfect, but had condemned him unheard; and this showed a much harder, far less affectionate woman than the Diana he had known or had thought he knew - a mythical person, no doubt created by himself. It had of course been evident from her letter, which made no reference to his; but he had not chosen to see the evidence and now it was absolutely forced upon his sight it made his eyes sting and tingle again. And deprived of his myth he felt extraordinarily lonely.
The protagonist reflects on Diana's swift judgment of him without seeking any clarification, revealing a harsher and more distant side of her than he had believed. This perception shatters the idealized image he crafted in his mind, leading him to realize that his view of her was a fantasy rather than reality. Despite his prior detachment from her letter's implications, the truth of her condemnation now overwhelms him and evokes a profound sense of loss.
As he confronts the reality that Diana is not the affectionate figure he imagined, he experiences a deep loneliness, compounded by the absence of the mythical version of her he had held onto. This revelation forces him to grapple not only with his unfulfilled expectations but also with the isolation that comes from disillusionment. The emotional sting of this realization underscores his vulnerability and the void left by the demise of his idealized perception.
