The main conflict in the story is Kugelmass's refusal to accept his own reality and his refusal to make his life better. He says that he wants something more exciting in his life, perhaps an affair, something exciting and "discreet." His therapist notes that his problems run deeper and implores him to continue his therapy in order to realistically fix his emotional problems. But Kugelmass, perhaps yearning to be young again, is discouraged that in his advancing age, his "options" in life are gone. He refuses to consider that his best (most realistic) option is to improve himself in order to improve his life.
Jumping into literary worlds, via Persky's magic machine, is not a solution to his problems; it is an escape. In fact, when Kugelmass gets what he wants (romance, flirtation, etc.) he is still not satisfied. Thus his problem is not solved because he has looked for glamorous solutions to his own psychological problems. If there is a symbol in the story, it is the animated Spanish verb "tener" which means "to have." Kugelmass had been chasing what he thought he needed "to have." The final irony is that he is being chased by the notion/verb of "having." Instead of dealing with what he already had, Kugelmass tried to have more and more. Because he was never satisfied, having never gotten to the root of his problems, he chased "having" so to speak. Fittingly, "having" ends up chasing him.