How does a writer deal with negative feedback?

You can use a negative feedback as a vehicle to improve your craft.  Or, you may just shrug it off if it does not help you.

Anyone in the Creative Arts has to be prepared for negative feedback, in fact you must expect and welcome them. More often than not, you would learn from some of the comments, especially constructive criticisms.

However you must know yourself and your craft so that you're not misguided or end up confused. But don't let the negative comments drown you while you sift through them, rather try to filter them. You must first know your target audience, and if the majority of the negativity is not from your target demographic then you can hardly be bothered. Although if you have no positive feedbacks, you have to admit that there just may be something wrong and you just need to see it as a challenge to learn more and practice more, then you can perform and write better.

First, by not letting negative feedback bring him down, then he can go through these feedbacks and see how he can improve his skills by overcoming them!