The critique group at Orbital was extremely helpful and quite encouraging. And it gave me a certain insight into how to take constructive criticism that I wish to all heaven I had figured out ages ago.
In my younger days as a writer, I dutifully took the short stories I wrote and ran them past a certain circle of writerly types in my acquaintance. Some of them had actually been published and I made the fundamental error of assuming that since they had ascended to the ranks of the published, they knew more than I did about how I needed to be writing.
I think part of the problem was, they were perfectly good writers, but not terribly good critiquers. One in particular (won't name names) had a tendency to suggest things that were How He Would Have Done It, even though the way he thinks and the way I think are so fundamentally different that we can debate the questions of the universe for days. Which makes for lively conversation, but not the best of writing advice.
Ponder this metaphor--you're picking out an outfit for a certain social event. You want to make a good impression, so you ask your roommate (for example) what she thinks of it.
"Hmm," she says, "First off, your shoelace is untied. And the pants look good, but I'm not sure if they go with the red shirt. How about that blue one you have?"
Finding mistakes in grammar, punctuation, et cetera, are the equivalent of "your shoelace is untied." They're things you don't always catch, especially if you've been staring at the same pages for ages on end, and those are always good things. (Something that's technically a grammatical mistake, but done for effect, might be the equivalent of "your jacket is all wrinkled" to which your response might be "Um, it's crushed velvet, it's supposed to be wrinkled.")
The blue shirt, is a little trickier. The blue shirt can be things like "this character seemed like a rather sensible type; why the hell did she suddenly decide to jump on the back of a motorcycle with a complete stranger after only three lines of conversation?" That's the moment that you notice that the red shirt has a slight pattern to it and the pants are pinstriped and one or the other has got to go.
There are different ways to react to a blue shirt criticism. Sometimes you realize they have a point, and the blue shirt really does work better. Sometimes they have a point that the red shirt doesn't quite work, but the blue shirt they're suggesting doesn't quite work for you either, though you do have this purple one that you try on and matches perfectly.
And sometimes you look in the mirror and think about it and decide that the red shirt is just fine. But you at least tie your shoelace.
It is probably best to find a critique group who has the same taste in clothes (if you will) that you do. At the very least, they should be familiar enough with your work and sensibilities to know what your mental wardrobe looks like.
But when it comes to writing, it really is best not to wear other people's clothes. They won't fit you properly or look right. Take the advice, try what fits and tailor it to what you're trying to create.