What frightens Holden continuously throughout the novel The Catcher in the Rye?

Holden Caulfield's primary fear throughout the novel concerns the inevitability of entering the competitive world of adults. As a neurotic, hypercritical teenager with a traumatic past, Holden desperately tries to cling onto his childhood innocence and avoid entering the world of adults. Holden's fear of adulthood is expressed through his extreme cynicism, judgmental nature, and jaded personality. He views the majority of adults as phonies but has a strong connection with his younger sister, Phoebe.
Holden fears becoming an adult to the point that he wishes he could become a catcher in the rye who prevents all children from growing up and becoming phony adults. In addition to Holden's fear of entering the competitive world of adults, he also fears that he will disappear. There are several moments in the story when he asks his deceased brother, Allie, to not let him disappear. Holden's fear of disappearing is associated with his fear of transitioning into adulthood and losing himself.
Overall, Holden fears entering the competitive world of adults, where he believes people are only concerned with wealth, status, and their reputations.