If you publish, you have to be ready to take criticism. It may come from an idiot in a crowd who wants to make himself look important, it may come from a well-meaning acquaintance who feels the need to point out an error that it's too late to change, or it may come from a clinical professional. However it arrives, criticism is like a needle under your skin, a short burst of pain and a lasting sting that is hard to ignore.
We want to be understood, and when people pick at our work, we feel they've misinterpreted it. Even when the criticism is justified, we want to explain it away, make the critic see why we did what we did. Many times I've heard people question authors about niggling points: why doesn't a street in the book look like it does in reality; why are distances compressed or illogical routes taken in a story, why don't the cops know that the victim was a heroin addict. To answer that I would quote a writer more famous (and more blunt) than I who says: "We're writers. We make shit up."
But the other criticism, the panning of one's writing, is even harder to take. Flat characters. Bad prose. Unlikely story line.
Ouch, that hurts. But like a hypodermic, it may be a point that delivers something you need.
The answer, as Brutus says in Julius Caesar, is in philosophy. Understanding that you won't please everyone is the most important thing a writer can learn. Understanding that some will phrase their criticism in the most hurtful way possible, often to make themselves seem intelligent, can help you deal with it. And maybe understanding that you don't have to read what they say could be the most helpful of all.
Someone liked your work enough to publish it. You liked it enough to lay it out there for the world to see. You're told that people enjoy it. Okay, so one person didn't. When the negative comes, there are three things you must do: listen to it, reflect on it, and then go back to doing what you do. If it's justified, the criticism will help you be a better writer, like a shot speeds you on the way to good health. If it isn't fair, the sting will go away eventually, and the incident will be, like the nurse says, "A little poke." Not eternal, just briefly discomfiting.