Your thesis sentence should include the specific theme that you want to discuss (choices have consequences) and a similar aspect of characterization between Sammy and you. Here is an example:

Just as John Updike's protagonist Sammy from "A & P" develops as he finds himself opposing an authority position, I too, recognized changes in myself as I challenged management in a retail store, specifically, as Updike discusses in his short story, that consequences accompany each choice one makes.

You want your thesis statement to be specific so that you can logically and seamlessly support the statement in your body paragraphs. Good luck!