Treat it like "gathering data" as much as you can. I know it's really hard in early days where you might not have made a lot of comics or novels, so the one or few you have are like "MY BABY!", but it's pretty likely that your comic or novel won't be the only one you ever make.
In the industry, rewrites are very common. In my day job, I help make these kids books with a narrative and activities, and the first one, the final draft for the text was draft 42, I'm not even kidding. It went through that many rounds of edits and so much feedback from so many people. Working on it really helped me get used to criticism, especially because everyone was having to do the same; the authour, the designer, the illustrator, all of us had to work iteratively and never assume anything was the "final version" or completely safe from being cut.
The media has an unfortunate habit of wanting to turn the story of a work's creation into a narrative, where the author or artist becomes the "protagonist" of the story, and how much they were directly responsible for both the work that went in and every creative decision gets exaggerated, and then everyone who ever challenged them at all becomes a rival or antagonist. The "baddies" all say things like "POPPYCOCK! There's simply no way your story will work! Nobody has ever attempted such a thing!" and then the hero shows them all through their amazing idea and hard work! ....Except that's almost never what really happened. The creator probably had a bunch of people who gave them useful feedback and advice; the people who said negative things or raised issues probably weren't all antagonistic and trying to stop them, and they probably went through a very boring and un-dramatic series of tries rather than blasting out the perfect final version in one go to an uplifting montage. If you hold yourself up to these fictionalised versions of what a creator should be, then of course criticism feels like a sign that you are failing, or you'll read it as an attack from an antagonistic force.
The truth is, nearly every great creator gets advice and feedback and goes through multiple tries to refine their work. You haven't failed if you get told something could be a bit better.
Feedback is important because your guesses and gut instinct for what works might often be right, but they can't always be right, especially when you're still learning or are trying a new medium, format or genre. Even feedback from people with no idea how to create themselves can be useful.
Generally if the person giving feedback isn't experienced in the field of specifically what you're making, it's best to listen to and note down things they point out as problems, but to largely not bother too much about their suggestions for fixes. As the saying goes in UX design; "Users are good at spotting problems, but bad at giving solutions". So a lot of the time, a reader will correctly identify that your comic is hard to read, or that it's dragging a bit... but then their suggestion to fix it will be something bad like "change the dialogue font to Arial bold" and "Cut out this character I don't like by killing them off!" So for solutions, it's better to look for somebody who is having a bit more success or has a bit more experience at the thing you're trying to do and either read or watch resources they've made or ask them for advice, and they'll probably help you out like "Ah, I see, you should make your text a few points bigger and increase the space between the text and the edge of bubbles" and "This part of the story drags because the stuff the characters said and did didn't change anything about their situation. Can you add some consequences that will affect a future scene?" because they probably already solved those exact problems in one of their past works, or got some good advice from somebody else!
Sometimes you'll get useless advice. Maybe the person is giving their totally uninformed opinion like "I like purple so I think you should have more purple in your comic!" (welcome to the hell of "when the client asks for suggestions from their child. This is a thing that actually happens). Sometimes the person is an expert in a related field, or even is an expert in your field...but has been out of the loop for several years (a common issue with university tutors) and thinks their advice is good, but it's actually not like "Ah, you're making a comic, eh? You should put in some of those thought bubbles to show the character is thinking! How will the audience know they're thinking if it's not in a cloudy bubble!?" because this person is from an older generation and has not been exposed to manga and modern webcomics which have a design language influenced by it for internal monologue, so they don't realise adding cloudy thought balloons would just make your comic look a bit old fashioned. Then of course, as you build a following, you'll get more and more people who will criticise your work, but not directed at you but at others, often telling them why your work doesn't deserve to be popular (and extra fun points if the implication is "doesn't deserve to be more popular than their own work") but they want it to be seen by you because you're "unfairly popular" and must need taking down a peg. Bad advice can sometimes feel very justified, so it's good to seek out multiple opinions for all criticism and to look at your options. There are usually many ways you could solve an issue, so seek out a bunch and find one you like, or sometimes there really isn't an issue and the person complaining just isn't your audience.
