Answer:
The main theme is that you have to be careful with what you wish.
Step-by-step explanation:
The main theme of story called "A birthday tradition" is that you have to be careful with what you want. For example, Justine didn't want to go to the movies with her grandmother, and she was hoping she wouldn't have to. However, she learned later that it wouldn't be necessary or even possible to do that because her grandmother was sick that day. Justine felt so sad about it and even regretted her previous rudeness and ungratefulness.