Sherlock Holmes seems to have retained a lifelong affection for Irene Adler because she defeated him at his own game, which was reasoning. Holmes did not have a high opinion of women in general because he thought they placed too much emphasis on emotion and were deficient in what was his forte and obsession. Irene Adler was the exception. He was the kind of woman he might have married--if he could ever find such a woman who would be willing to put up with his eccentricities. According to Dr. Watson:
All emotions, and that one particularly [love], were abhorrent to his cold, precise but admirably balanced mind. He was, I take it, the most perfect reasoning and observing machine that the world has seen, but as a lover he would have placed himself in a false position. He never spoke of the softer passions, save with a gibe and a sneer. They were admirable things for the observer—excellent for drawing the veil from men's motives and actions. But for the trained reasoner to admit such intrusions into his own delicate and finely adjusted temperament was to introduce a distracting factor which might throw a doubt upon all his mental results.
The famous psychologist Carl Jung, in his book Psychological Types (1921), repeatedly asserted that thinking and feeling are mutually exclusive. A person whose conscious functions emphasize thinking will be indifferent to feeling and will seem cold; whereas a person whose conscious functions favor feeling will be weak in the area of reasoning. This certainly seems true of Sherlock Holmes, although it does not necessarily seem true of Irene Adler. She was a woman who displayed feminine feelings but could also "think like a man." In fact, she could think like Sherlock Holmes. That made her a dangerous opponent. She ended up defeating him in his attempt to retrieve the compromising photograph of Wilhelm Gottsreich Sigismond von Ormstein, Grand Duke of Cassel-Felstein, and hereditary King of Bohemia.
The case turns out successfully in spite of everything. When she flees from England with her new husband, she leaves behind a letter addressed to Mr. Sherlock Holmes in which she writes, in part:
As to the photograph, your client may rest in peace. I love and am loved by a better man than he. The King may do what he will without hindrance from one whom he has cruelly wronged. I keep it only to safeguard myself, and to preserve a weapon which will always secure me from any steps which he might take in the future.
Although it may be true, as Watson says, that as "a lover he would have placed himself in a false position," Holmes is involved in many cases in which he is motivated purely by sympathy for a young woman in distress. These include the young female clients in "The Adventure of the Speckled Band," "The Adventure of the Solitary Cyclist," and "The Adventure of the Copper Beeches."