So far we have been very lucky with Angelica when shopping at the supermarket. She seems to understand very well when we tell her that we will not buy everything she wants. For example, the other day, she grabbed a box of Smarties, but quietly put it back on the shelves when we told her that we would not buy it because we already had some at home, and that we would give her some later.
I think our parenting style has a lot to do with her reaction. We don’t lie to her. When we tell her “one last bite,” we mean one last bite. We will not come back with another “one last bite.” We also try to give her an explanation she can understand whenever we say no. In the case of the Smarties, we did give her some when we got back home as promised. We don’t always say no either. When we feel that she deserves a treat, we will give her. If not, we will tell her “not this time” or “next time.” And most importantly, in our opinion, we let her explain why she wants this or that, and not just say “because we said so.”