As an adjunct to my writing career, I teach writing to young adults and adults, in various venues. (I did the same in my musical career, as many singers do--the income from concerts and operas can be variable, and it's nice to have a steady income stream from somewhere!) At the moment, I'm doing distance learning for the excellent Long Ridge Writers' Group, a beautifully structured course called Breaking Into Print.
There are people for whom the nuts and bolts are just really, really hard. For those of us who think in terms of language, who love to play with words and punctuation, similes and metaphors, these nuts and bolts come as naturally as breathing and swallowing. Where to put a period, when to start a new paragraph, when a sentence fragment works--these aren't the big issues we deal with. But for lots of people who yearn to write, and in fact, have something important to say in their writing, these are hard issues to grapple with.
This isn't a matter of intelligence, either. I know doctors and nurses and engineers who are way smarter than I am, in their area of expertise. But language is its own skill. Its own talent, I should say. It's rather like classical singing--the desire to do it, even possession of a good voice--isn't enough. There has to be that "genius", if you will, that knack for it.
I don't know, yet, how much of this can actually be taught. I certainly came to know, in teaching singers, that for some aspirants the whole process just never comes together. But as I watch the sincere effort and dedication of some of my students, I really hope that my attempts to teach them where the comma goes (and where it doesn't) are helpful. And their struggles remind me not to take my own talent, such as it is, for granted.