I got dumped on. Another writer read the entirety of a manuscript of mine and came to the conclusion the the protagonists was completely unlikable, the antagonist was made of cardboard, the plot had no logic, the dialogue was on the nose, and she didn't like it very much.
Oh, but some of the descriptions she'd found confusing earlier were clear now. Have a nice day.
So far, this is the ONLY reading of this full manuscript so, even though I've gotten lots of praise for portions of it by many other people, I was knocked off the rails. I actually stepped away from the work, and I have applied my efforts to another project.
Now my critic in this case didn't like the portions she'd read before, but, even though I have made my living writing for decades, I let it get to me. In part. It did not stop me from writing, and I will get back to the manuscript in question no later than February 15. I know this because it is written on my calendar.
So my first tip is be prepared for disaster. In this case, I had a fallback plan of another manuscript and a specific date to resume work. Critiques can do more harm than good. I've seen people both give up writing and avoid all feedback as the result of a scathing review, comment, or contest score. Mostly, this feedback was unjust. And even when every criticism is justified, that feedback says nothing about the writer or other works. Marvelous writers create clunkers all the time. So what.
My second tip is show gratitude. I will thank the woman who reamed me out. After all, she took the time to read my whole manuscript. Judging from her reaction, those hours were torture. She deserves my thanks. Selfishly, however, it requires me (a calmer, more prepared me) to look over her comments again and see if I can discover something specific that is of value.
I began to do this as a regular practice when I was entering a lot of contests. It's easy to be overcome by a wide range of often conflicting comments when you submit works into competitions. The temptation is to wallow in the compliments and reject the rest. I forced myself to write thank you notes citing the value I got for everyone who offered more than a score. It wasn't easy, but it led to my getting a better understanding of where I could improve.
Tip #3 -- Listen, but don't do what they say. People are very good at putting their fingers on problems. They know when they got bored or confused. They react when they think you pulled a cheap trick and cheated them and the story. And if more than one critic has the same problem, it is almost certainly time to try it a different way. But what readers, even those who are writers, do not do well is prescribe solutions. No one knows the intent of the story as well as you do. So grabbing at a proffered solution is usually a mistake.
Tip #4 -- Sometimes they really don't get it. I knew a marketing person who kept a stack of T-shirts in her office that she would throw at executives when they complained about a promotion. They said, "I'm not the target audience." Your best move is to not give a writer who loves romances and hates SF your latest space opera. And don't give your passionate historical novel about love between a Boston Brahmin and a refugee from the Irish famine to technothriller fans. It just won't work.
With that said, you may put your mystery into the hands of an avid mystery fan and it may fall flat. If that happens, do not assume you have failed. There are horror readers who hate everything Stephen King writes and SF devotees who are deaf to Terry Pratchett's humor. So put their review aside, go out and get more feedback and suspend judgment of your work until you hear what others have to say. That's what I've done with my latest dose of poison.