Holden's fantasy about being a catcher in the rye, a sort of guard whose responsibility it is to look after children playing in a big field near the edge of a cliff, is not realistic, but it certainly is poetic. It is also panoramic. It shows a mind with a vivid imagination and a broad scope. He could never be a catcher in the rye, but his fantasy suggests that he could find a career that was related to that image. He could become a pediatrician, for example. Or he could become a social worker who handled cases of children who needed help, such as orphans, juvenile delinquents, and abused children. He could also become an elementary school teacher. A person with his imagination and verbal skill could become a successful writer of children's books, and one of those books might be about a giant who stands in a big field of rye grass watching over children at play. In fact, it is a wonder that nobody has ever written such an illustrated book based on Salinger's novel. Holden is at an age where he is strongly interested in sex. But sex is intended for procreation, and his fantasy might represent an unconscious desire to become a father with his own children to nurture and protect. It seems to me that the image of a catcher in the rye is one that comes out of his unconscious. Holden is an intuitive person, which means that he relies on messages that come to him from the unconscious part of his brain. These messages are not usually literal but are more like dreams which need to be interpreted, or like promptings to think in a certain direction. Holden should take his fantasy seriously and use it to guide him in choosing a practical career.
Holden's desire to become a catcher in the rye is not a realistic goal, it is part of his fantasy life, something that he must leave behind if he is to have a stable, successful life.
Holden's biggest problem is that he won't recognize reality, he rejects everything based on a mistaken belief that he can create his own truth. Holden believes that if he views adult behavior as phony then he does not have to engage in responsible behavior because he refuses to engage in phony behavior.
This is a misconception on Holden's part, grouping all adults as phonies, therefore, resisting growing up. Putting aside the fact that I believe that Holden is suffering from clinical depression and unresolved grief, it is easy for him to hide behind his outrageous opinion and imagine this fantasy job as catcher in the rye.
Holden's notion of "catching" children playing in a field of rye before they fall off a cliff is not realistic in the least. The entire idea is completely imaginary, based on the song he hears the little boy singing. Holden's need, however, to protect those he perceives as innocent and vulnerable, such as the ducks and Phoebe, stems from his feeling of helplessness because he was unable to save Allie. He could not prevent a young child's death. As a result, Holden wants to protect all children from the dangers of the world in any way he can. For instance, he seeks to eliminate the obscene language he finds at Phoebe's school.
Eventually, though, Holden realizes that his goal is unrealistic. While he watches Phoebe on the carousel when she reaches for the gold ring and worries that she may fall, he understands that he has to let her experience her own failures. If she falls, she falls; he has to let her. Holden cannot protect her forever, and he finally accepts that fact. He sees his desire to be the catcher in the rye as unreachable and unrealistic.
His ambition to become the catcher in the rye is not realistic. In his perfect reality, children would stay forever and him being the "catcher" represents him catching children just before they move onto a darker world aka the world of adulthood. His dream is unrealistic because there is no way to stop someone from growing up, one way or another they will end up losing their innocence, of course not completely but still. His idealistic world is very hard to attain, therefore making his dream unrealistic.