It seems like such a silly thing to regret now, writing a blistering criticism of a college paper submitted by a classmate. I can't even remember her name. I do remember shelling her story with verbal bombs and not offering any worthy ways to improve, and I'm sorry for that.
One of the largest parts of a writer's life is hearing all about what you did wrong in a piece of writing. It's part of the larger attitude of society that looks down on writing as something that is worthy of being a career. I've written about it before, most people think that writing isn't all that difficult, conveying your thoughts onto paper is something almost anyone can do. Therefore, it's fine to heap scorn on those who want to be taken seriously.
Consider me as guilty as the next person. I took an entirely predictable romance story which wasn't poorly written (though it would never be mistaken for polished writing) and tore it to shreds, based almost solely on the sappy romance plot. The girl who has a best friend that's a boy growing up, constantly rejecting him until one day it dawns on her that he's really the one.
I railed against the predictability of the plot, which is the among the least useful criticisms I've ever offered to a fellow writer, and I wasn't kind about how I said it. I didn't learn a lesson from this episode right away, but rather karma took down my name and circled back a few years later.
It is the great misfortune of any writer to find themselves working as a reporter for a small town paper. The pay wasn't great, and it was certainly unequal to how I was treated on a daily basis.
"Nothing but lies in that paper," people would say. "I only buy it for the police blotter and to find out who died." (I did take solace that I wrote both of those things as well.)
If I would ask what things would make the paper better, people were always at a loss. Rarely did that ever even get a response, let alone one that was coherent and reasonable. That's when I finally started understanding the fine art of criticism, both giving and receiving it.
The first thing I would say to any writer who is down on hearing a particular piece of criticism is to consider the source. At least half of the people offering negative feedback are either unqualified or have their own agenda. These are often modeled in the same ambiguous way that people would criticize the newspaper. Just because a reader doesn't personally "like" what is written doesn't immediately make it bad. This was true for sure in my reporting, and still holds true for my other writing.
I categorize this as "choosing the wrong audience". This is what happened to me back in college. Her story wasn't meant for someone like me. If another writer asks for feedback and the writing falls outside your interest zone, you have to get past your own dislike of the plot to analyze the writing. At worst, you should at least help the writer understand what audiences they should be targeting.
You will also occasionally encounter people who are obsessive-compulsive about grammar and structure. A good writer can separate out legitimate things from personal preferences. As someone offering a critique, you also have to take a step back from your own style and try to understand what the writer is trying to accomplish. A character might be using poor grammar as a personality trait (reflecting on being a poor student in their younger years). Someone might like long sentences, conveying different, related thoughts with large blobs of words between periods. Others like short ones.
Criticisms on style or grammar have to be weighed for what they're worth. You might use lousy grammar on purpose, as part of a writing or narration style. Other times, maybe you just plain made a mistake. In offering criticism, it might help to explain why stylistic things don't work in a particular instance, such as a character who wins a grammar bee then celebrates their win with a dangling participle (unless it is for comedic effect.)
Over all, the goal of criticism should be to offer help whether you are meting it out or grudgingly accepting it. Things that don't meet that litmus test should be thrown out. It's ok to ask someone why they reacted negatively to your writing to help you make that judgment. And when you're offering a critique, you should always give care to think about how you would like to be informed of the flaw you're pointing out.
I feel it's important as a writer to learn how to give and take criticism, since it really is such a large part of the profession.