We've all heard it before: "I just didn't like your book." No matter who says it, or how they say it, it just doesn't feel good. It makes us feel inferior, and like all our hard work was for nothing.
If you're lucky, this negative comment came with some constructive criticism. You should always welcome constructive criticism, as it can only help you improve your book. Even if you feel a bit hurt, you should be glad someone took the time to tell you how to make your book better. They cared enough to offer suggestions, so you need to thank them and consider them.
Be careful with those suggestions, though. First, you need to consider where the suggestions came from. Are they from a trusted editor (or Inkpop user)? Does this person actually know about writing, craft, and how to write a good story, or are they just making stuff up? If they know what they're talking about, great. Use their advice, but don't follow it blindly. After all, you know your story better than they do. For example, they might suggest you focus more on the romance aspect of your historical fiction novel. But, while the romance is part of your book, you don't feel that it needs to be the most important part. This is fine; everyone will have a different opinion of your book, and you can't please everyone. Use your own judgement, in the end.
We all know that "It just didn't work for me" or "I'm sure many people could enjoy this, but not me" or "It could be good, if you change this and this and *basically the whole thing*" are just a nicer-sounding way of saying "I didn't like this book at all." It would be stupid of me to tell you to not take these things personal, because we're writers. We do take it very personally, but we have to learn to not let it get us down.
I look at it this way: I wrote my book so it could be enjoyed. If someone doesn't like it, then they are the ones who suffered, not me. It's their problem, not mine. This way of thinking seems to work well for me, though I'm not saying you should ignore constructive criticism, because you shouldn't. It just helps me be able to take the criticism and use it in stride, without letting it crush my self-esteem.
I can promise you one thing. There will be someone who hates your book. I can guarantee it. There will always be someone who can't connect with the characters, who finds the plot dull and flat, who thinks the prose is ugly. And they will make these facts known.
You have to take these negative reviews in perspective. After all, how many positive reviews have you gotten? Read carefully: the good outweighs the bad, doesn't it? Which means that your book is more than that nasty reviewer makes of it. You are more than that, and so is your writing. Focus on the positive, not the negative.
God forbid you ever get an overly nasty, rude, inappropriate, harsh review that simply bashes your book mercilessly. This isn't an acceptable way of reviewing books, but it does happen. And you know what? These reviews mean nothing to you. No intelligent reviewer would act that way. Simply toss these reviews out the window and forget about them, because they honestly aren't worth your time.
You can't let any review, whether it is constructive or not, get you down. You are a strong writer; you can learn from your mistakes, and pull yourself up again. You just have to take each review in stride. Learn from your mistakes, but let yourself take praise when it comes.