In "The Case-Book of Sherlock Holmes," Arthur Conan Doyle reflects on the solitude experienced by Sherlock Holmes after Dr. Watson leaves him. Watson's marriage marks a significant change in their partnership, and Holmes feels abandoned, viewing this decision as the only selfish act in their long association. His feelings of loneliness underline the deep bond they shared and highlight the impact of Watson's departure on Holmes's life.

This moment reveals Holmes's vulnerability beneath his stoic exterior, as he grapples with the loss of his closest confidant. The quote encapsulates the complex dynamics of their friendship, emphasizing how even a brilliant detective like Holmes can feel isolated without his trusted companion by his side.