Walking out of the A & P, Sammy knew he had made a mistake. Three young ladies, clad only in skimpy bathing suits, had entered the store shortly before. As they cruised up and down the isles he admired them in the way any teenage boy would. He was working then, and as luck would have it they came to his slot to complete their purchase. Stepping over from his office, the manager, Lengel, informed the girls that such dress is inappropriate and that they must be decent upon entering the store again. Sammy stepped forward defensively and quits, hoping the girls would take notice. Even after the girls kept walking, and Lengel had given him a chance to take back his resignation, he took off his apron and left his slot, recognizing "how hard the world was going to be to me hereafter." This story, "A&P," by John Updike suggests that adolescents often act impulsively, and that growth comes from accepting the consequences.
From the thoughts and actions of Sammy, it is easy to determine this central idea. Sammy becomes enamored with the girls, and Lengel's admonishing upset him. In his mind, the girls were making a statement of beauty, and existed on a higher plane, free of the codes of the average grocery shopper. He resigns in an attempt to defend their honor, but recognizes his folly when they leave without giving him so much as a glance. By his own admission, his action would make things difficult in the times ahead. It is clear Sammy understands his mistake, and will not act so foolishly again.
Walking out of the A & P, Sammy was at terms with his bad decision. Soon to leave the teenage years, he was already maturing and as Updike points out, without making mistakes one cannot mature.