What are some lessons that Sammy learns throughout the story "A&P"?how does his character evolve
Sammy acts in haste in the beginning of the story, quiting his job to prove a point. He is opposed to the way the manager treated the girls who came into the store wearing bathing suits. He wants to look like a hero to these girls, so he acts without thinking about the consequences that will result from his decision.
"The girls, and who'd blame them, are in a hurry to get out, so I say "I quit" to Lengel quick enough for them to hear, hoping they'll stop and watch me, their unsuspected hero. They keep right on going." (Updike)
After Sammy makes his grand gesture, he is not even noticed by the girls who briskly walk away, leaving him to reconsider his actions. He again says that he quits. He doesn't like the store, he has no respect for the customers.
By the end of the short story, Sammy has learned a very valuable lesson, act in haste repent in leisure. In other words, think carefully before you make such a big decision, think beyond how good it feels to say the words. Although Sammy gets a momentary feeling of justice with his words "I quit," he is left with the result of those words.
He realizes that he should be careful in the future. He understands that jobs are valuable and should not be cast off with such ease.
"His face was dark gray and his back stiff, as if he'd just had an injection of iron, and my stomach kind of fell as I felt how hard the world was going to be to me hereafter." (Updike)