Why do certain words make a difference?

It is the eternal question of a writer. How do I make my story matter? How do I make something that is important to me, feel important to everyone else? My dog died, but why would you care? If I have learned anything from the past couple years of studying under excellent writers, it is not the situation, but the story that makes the difference. If Susan Sontag can keep me intrigued through an entire essay of different definitions of "camp", we can make anything interesting. Unfortunately for me, structure is one of my biggest issues as a writer. I know exactly what I want to say, but I can't for the life of me know WHERE to say it! My impact ends up being entirely at the beginning, drawing the reader in but never keeping them. I want to matter to people, and for them to have that resonating feeling that Vivian Gornick has after attending the doctor's funeral. An important part of this is making every word count. My job has recently involved sitting down with an English professor to write emails that I would otherwise not think twice about. Requesting videos from a vendor that we've used before, asking students when a convenient time would be to meet...things that would take me barely any time. However, as I backspace and re-type phrases multiple times, I realize that every word counts, even in something that seems rather meaningless to me. She asks my opinion on which phrasing seems best because even words in short emails reflect how apt the person is to respond, or how important that they are noticing this situation is to the person sending them the email. It is vital to figure out what you are trying to convey before you try to say it. And though I know all of these things, the difficulty is applying them when it's time to write. I know that I have poor structure but I continue to place things where I want them instead of where they make sense. I know that every word matters but I instead vomit out sentences that mean something different than what I had intended. Instead of reliving the entire story, I recall most of it.
With nonfiction, things are more complicated than fiction. As Gornick notes, the unreliable narrator is perfectly acceptable but in nonfiction, the reader must believe the narrator. This is also difficult for me, like Hunter S. Thompson, because of our eccentric and frequent drug use. When I see moving, colorful stars on the ceiling...I'm seeing them, but that doesn't necessarily mean that they're there. I must find a proper way to differentiate reality from MY reality. I need to find the right voice, the one that makes the reader aware of what is happening without taking myself out of the vivid reliving of the moment. I have to create a persona, someone who can tell the story for me.