Can't Punctuate Dialogue? Consider the Sentence

Whereas everyone is welcome to write without a clue - you do have a computer, after all - unless you start with a strong foundation and build from there, your lack of understanding is going to cost you. 

Recently, a student of mine expressed strong irritation when I suggested she learn to punctuate. Yes, I really am that annoying person. Well, the next time I went through her writing, I restrained myself from spending the time and effort on such minor matters as how her sentences were put together. I should simply presume people will be happy to pay for an edit rather than learn some of the basics of writing.

I thought I might start here with the sentence, really for a reason that has to do with punctuating dialogue - the issue on my mind right now. Why? Because while line editing, I've found so many examples of a certain glitch that boils down to a mere misunderstanding of what a sentence is. Now, straightaway to it. (Of course this isn't a complete sentence, but that's beside the point...)

Here we go - and please approach this believing that comprehension will be easy and you're sure to grasp what I'm saying:

"Yes, you see, but I'm from the future. Not just my future, but your future too," Nora swallowed and her heart pounded, nearly pushing out of her chest. She wasn't sure that Jake would take her seriously. 

Okay, that's part one of the mistake I'm discussing. The question is, where does that second sentence end? With a comma, we indicate a sentence will go on. Therefore, what is the punctuation here saying? It's saying that the sentence is: 

Not just my future, but your future too, Nora swallowed and her heart pounded, nearly pushing out of her chest.

Does that look like a sentence to you? It's not a sentence - it's a mess. The hero of our story is the editor, who rushes in and places a period at the actual end of the sentence:

"Yes, you see, but I'm from the future. Not just my future, but your future too PERIOD" Nora swallowed and her heart pounded, nearly pushing out of her chest. 

AHA! Now we have packaged the actual sentences separately. And that's why we don't use a comma with actions or explanations after the dialogue. We do not by kneejerk put a comma before the end-quote mark. Because we don't know yet if the sentence has ended. Maybe yes, maybe no. 

"Yes, you see, but I'm from the future. Not just my future, but your future too," Nora said PERIOD She swallowed, and her heart pounded, nearly pushing out of her chest. 

How simple is that? We have to know where the sentence ends. At the end of the sentence, we place a period. Otherwise, we're continuing on.

Here's part two of the glitch.

"Yes, you see, but I'm from the future. Not just my future, but your future too." Nora said. She swallowed, and her heart pounded, nearly pushing out of her chest. 

Thus the person who thinks the sentence is simply ended before the "Nora said" creates a separate sentence where none is wanted. This individual doesn't realise that the quoted dialogue flows on to the attribution. 

I'm not saying that this individual is you - probably not, and you probably stopped reading when you saw where I was going with this. Oh, well. But maybe I've worked off a little steam. 

The error - this set of errors - is extremely common. I just edited a 500-page novel in which the author avoided the mistake perhaps three or four times. Don't be that person.