Question: What's the difference between watching four 30-minute TV episodes and one 2-hour movie in one sitting?
Answer: The feeling that the plot is entirely connected in the movie.
Aristotle calls this "unity." He says that, for a plot to have unity, all events must be connected by cause and effect.
Thought Experiment #1
Imagine starting each paragraph of your essay (besides your intro) with "Because of this..."
If we know what "this" is in context and see how it leads to next event, your plot has unity.
If you rely on time (or space) transitions, your plot doesn't have unity.
Thought Experiment #2
Imagine seeing a Marvel movie with your friend. After, your friend says, "That was great! But I lost track—how many days passed in the movie?"
You'd be like, "What, are you dumb? That doesn't matter."
What is a case study?
You don't have very many words for your essays. The broader your timeframe, the less depth you can go into. Your essay will be less memorable, and you'll make mistakes like the "I realized" trap to save words.
Your essay should start at the moment your main goal or problem forms.
It should end shortly after the goal or problem is accomplished or solved.
Doing this centers your essay around a single case study.
Intro (25% of essay): introduce the goal or problem and thematic trait
Process (60% of essay): how you improve at the thematic trait
Conclusion (15% of essay): your success, which implies your personal growth
The power of a case study
A case study represents a broader period of growth by turning that growth into a theme.
Example: If you want to talk about how you became more confident over the past six years, give a single example of a goal or problem that required a confidence you didn't originally have. This turns confidence into the story's theme.
I talk more about this in my guide on the three characteristics of the quest.
You don't have to tell your story in chronological order. If any information from your past is crucial to the story, you can give a short summary somewhere later in the essay as backstory.
For more info, see my guide on deleting your intro.