Writing for publication and rejection go hand in hand. You won’t escape it. The question is how to deal with it when it happens. Eating chocolate might help for an hour, but eventually you’ll need a new strategy, or face the consequences—a bigger rear end to put back in the chair.
First of all, it hurts, especially in the beginning. Let yourself cry if you need to, but don’t stay there for long.
Next, get yourself back on track mentally. It helps to have a catch phrase. Something you tell yourself to remember it was only one person’s opinion. It might be a strong compliment you received about your writing, or a short phrase that reminds you that rejection happens to even the best manuscripts. It can be something as simple as “Harry Potter.”
A close friend of mine had a temporary job at a publishing company years ago. Her job was to read manuscripts. If she didn’t like a submission, one other person would read it before it would be rejected entirely. Harry Potter was among those manuscripts. She was the first one at the company to read it, and she made it clear she didn’t like it. Her superior read it and also rejected it. Needless to say, they are both still kicking themselves.
Yes, we need to learn from our rejections and seriously contemplate any criticisms. On the other hand, we must not let them be the last word. It may be that your manuscript hasn’t fallen into the right hands just yet. Keep on submitting!