The problem that I referred to yesterday regarding atmosphere and point of view may be illustrated by considering what you would omit from your diary entries. Consider how someone who is not familiar with our modern world would interpret a typical day. Let's have someone from the Roman Empire read a line from your journal.
I woke up at 7:00 so I could drive to school for my first class.
How many things would you have to explain to give a full picture of this line to your Roman reader? Instead of a full narrative, just make a list. Any list I make will have holes in it, but here are a few things. Some of these concepts would have rough analogies, but would need further explanation. You might be able to picture the Roman reader asking one question after another, leading to the various concepts.
Modern reckoning of time
Electricity (the physics/chemistry)
Electric wiring of houses
Electric power generation using fossil fuels
Drilling for oil
Solar power and alternative fuels (and current marketplace irrelevance)
Electric power wiring infrastructure of cities
The modern corporation
Public utility price regulation
Speed of automobiles
Assembly line techniques
Modern university education is specialized
Modern university education is for nearly everyone, not just a small percentage of extremely wealthy individuals
Mixed public/private financing of education
Modern social structure
Modern views of gender
Human capital theory. That is, most university education is sought in order to increase the individual's expected future income (it was not always this way)
I will stop there. You would not think to explain all these concepts in your journal. In fact, I could not competently explain them all. If you did take time out to explain them to your Roman reader, it would be clear that you were not telling a story as you would naturally tell it.
How would you explain any of these concepts? Some of the concepts have analogous concepts for our Roman reader--some don't. An automobile is like a big chariot, which uses a device to give it power (opening up all those questions). Electric wiring of houses and cities is like the aqueducts and public water distribution systems that some major Roman cities had--only for electrons (eesh!).
In fact, you may not understand many of these concepts. I do not have enough familiarity with physics to feel comfortable explaining how spinning a magnet inside a coil of wires generates electric power. Any physicist reading my last sentence is probably banging her head on her computer screen.
I feel more confident about explaining human capital theory vs. screening theory in education. That is, (human capital) does the university actually teach you things that make you more productive on the job? Or (screening) does the university just provide a difficult challenge that requires intellect, problem solving ability, and perseverance, so that students who can and will navigate the university maze and get a degree has shown that they will be good employees (though they learned nothing useful in the maze).
You can see that your Roman reader would need a great deal of explanation to get a full picture of what was really happening in your sentence. And if you provide these details, you won't tell much of a story. But if you change the time to "shortly after dawn" and change "drive" to "went," your Roman reader might have a clear (and terribly unrealistic) picture of what transpired and you can get on with your story.
Authors must satisfy themselves that they know enough about their world to tell others about it. Then they must tell enough so that the reader can understand the world without getting bogged down in the details. And the author's narrator (depending on the point of view that the author uses) must relate the important aspects of the world in a natural fashion.
My pet peeve involves modern writers who feel they have to describe every mundane traffic route from one location to another. "I took the 101 to the Santa Bozo Freeway until I was nearly to Plotzville. Then I drove west on highway 42 for five miles and took a dirt road until I saw a man standing beside the road with a sign that said, "Shut up. We don't care how you drive to work."