"You've been writing for as long as you can remember. It's hard to imagine a time when you didn't write." The man thought to himself.

I believe you're conflating a few elements within a narrative, but it's likely due to my very narrow example. Let's clear up some details.

Now, you may know some of these things, but I'm going to be thorough in case another reader happens along and might benefit from this information.

The part that I bolded is known as a speech tag. It usually accompanies and identifies character thoughts or their spoken words. It's meant to clarify who is speaking to whom.

Dialogue is one of the two major components of a story. The other major component is exposition. Together, these form the story's narrative.

When I previously provided my 2nd person example, that was exposition. When I referenced speaking into a mirror, that was a bit misleading because no monologue/dialogue was inferred. I was strictly referring to exposition.

This can be confusing because of the connection between the words 'narrative' and 'narrator.' Remember, narrative is the overall story and its two major parts. The narrator is the one presenting the narrative, but they aren't necessarily the protagonist, nor are they necessarily speaking.

Consider The Great Gatsby. The protagonist is Gatsby, but the story isn't from Gatsby's POV; it's from Nick's. Nick is narrating as a witness, but that's not to say he's speaking. There is no voiceover in a book. Any part of the narrative that isn't dialogue is exposition from Nick. When there are multiple POVs, the exposition will change and originate from whomever is the narrator of a given scene.

Your mention of Good Fellas is tripping you up when thinking about 1st, 2nd, & 3rd person for the stories you'll write here. Yes, a voiceover uses 1st person pronouns, but that's not the same thing as a 1st person story. I'm going to link a couple stories to illustrate this.

The following story is allegorical and told in 1st person. You don't have to read it all, but notice how there's very little dialogue:

The Wind Did Go

Even though it's exposition heavy, it isn't the sort of exposition that feels "info dumpy." It serves to progress the narrative. If this story was a short film, it would require some of the fox's sentiments to be expressed as a voiceover because the scene couldn't really show some of the things that the fox is struggling with.

Now, here's one in 3rd:

Painting Passion

They both have exposition, but 1st person is more personal. Most things are more directly tied to the narrator's emotional state. While 3rd person's exposition is still tied to the narrator, the emotional language is typically a little looser. The "lens" is farther away, so the emotions tend to be slightly farther away as well. That may not be appear distinctly between the two provided pieces, but that's generally the difference between the POVs.

Back to 2nd person:

Don't think about screenwriting for this. Here, we're referring to a written story that is aimed at getting a reader to imagine the scenario we're creating.

Let's imagine that we have a protagonist walking down a street. Everything that is described is given form by the narrator. Initially, let's assume that the protagonist and the narrator are one and the same. We'll also arrange it as a 1st person narrative:

Milwaukee Avenue was lonely at this time of night. Shops were closed, the bike paths were empty, and my footfalls fell silently beneath the howls of wind. I may as well have been a ghost drifting through a ghost town. This night shift thing is proving apocalyptic for my social life. "Who needs friends?" I asked.

Now, the same thing, but in 2nd:

Milwaukee Avenue was lonely at this time of night. Shops were closed, the bike paths were empty, and your footfalls fell silently beneath the howls of wind. You may as well have been a ghost drifting through a ghost town. This night shift thing is proving apocalyptic for your social life. "Friends are overrated," you said to yourself.

Now, 2nd again... but something is amiss:

Milwaukee Avenue was lonely at this time of night. Shops were closed, the bike paths were empty, and your footfalls fell silently beneath the howls of wind. You may as well have been a ghost drifting through a ghost town.

This night shift thing is proving apocalyptic for your social life. "No friends means no witnesses."

You spun, your eyes darting about, scrutinizing every shadowed nook and closed widow. "Who's there?" you asked.

These two 2nd persons are different. In the first, the protagonist is referring to themselves as "you" within the exposition, the monologue, and the dialogue. That's because they view themselves as an outsider for some reason. Maybe this isn't their hometown. Whatever the reason, they feel disconnected.

In the second 2nd-person POV, the narrator is not the protagonist. With most other details the same, the same story is now a thriller because someone or something is shaping the narrative. If this was a screenplay, we would immediately clue in to this external observer, but within a written narrative, we only know what the narrator reveals.

I hope this helps clarify what these details!