In "A&P," the mood shifts: it feels light, apprehensive, aroused, nervous, triumphant, and finally extremely apprehensive. Initially, Sammy's mood is relatively light. He at work and the day is quite typical except for the girls in bikinis. Now, he does imply that the other frequent customers find the girls' attire too risqué, and therefore this creates a rise in tension for those customers. Sammy is aroused by this spectacle and by Queenie in particular. Externally, Sammy plays it cool. His behavior remains somewhat light as he jokes with Stokesie about this rare sight at the A&P. But with the uncomfortable customers and Sammy's intrigue, the mood shifts with rising tension.
Sammy tells us when the mood shifts again. He notes,
Now here comes the sad part of the story, at least my family says it's sad but I don't think it's sad myself.
Much to Sammy's delight, the girls come through his line, and Queenie produces the money from her top. It is at this point that Sammy adds,
Then everybody's luck begins to run out.
By "everybody," Sammy means himself, the girls, and probably Stokesie to some degree. Lengel scolds the girls, and Sammy smiles at his repetition. Lengel wants to uphold a traditional, conservative 1950s public code of behavior, and Sammy, out of attraction and inclinations of social rebellion, wants to at least try out a more liberal 1960s culture of free expression. So he sticks up for the girls. That sounds a bit deep for this encounter, but below the surface, that is what Sammy's thought process might be.
During this confrontation, Sammy adds that everyone is getting nervous. This is classic rising tension en route to some climax. The girls leave, and Sammy abruptly quits, hoping the girls recognize his heroic gesture. They don't. Sammy has noted this is the sad part of the story, but that is according to his family, who had assumed he had made an irresponsible decision. For Sammy, there is some sadness that the girls miss his gesture. But more importantly, he feels this was a real moment of rebellion for him. Having left the more conservative culture of his parents' (and Lengel's) generation, he is full of apprehension, perhaps some excitement, and maybe even dread at how his life will become:
. . . and my stomach kind of fell as I felt how hard the world was going to be to me hereafter.