When feedback is constructive and helps you achieve what you set out to achieve it's terrific.
When it's destructive or a rejection, it can get to you if you let it. However, there are ways to cope.
One method comes from an illustrator I admire, Jeff Fisher (his images illustrate this post). What annoys him most is clients who hire him to use his creativity but then micro-manage the job.
He says, "I get annoyed with fussy clients. I write cross letters and emails--they calm me down. I draw over the letters and make a piece of artwork out of them, then usually throw them away. It makes me feel better." (Quoted in Making Great Illustration, Derek Brazell and Jo Davies. By the way, the place you are most likely to have seen Fisher's excellent work is on the cover of the paperback of Captain Corelli's Mandolin.)
A method I recommend is to imaginge yourself a month from that point. Will the rejection or criticism still sting? What about six months? What about a year? What about five years?
If you are strongly visually oriented, a way to make this method more powerful is to imagine the rejection filling your full field of vision right now--probably that's how it feels.
Then imagine it as a much smaller part of the picture six months from now, because you'll have all kinds of other things you'll be thinking about then.
By the time you imagine all the things, both past, present and future that you'll have on your mind half a year from now, today's thought will be just a tiny dot.
When you return to how it looks today you may be surprised to find it has already shrunk.
If you are more auditory, do the same thing with rejection as a voice or sound. Right now it's loud, but what will it sound like in a month, three months, six months? At each point in the future there will be many more things to hear, and today's roar will turn into a whisper.
You can do the same with a feeling. Today it's strong, in the future it will be just one tiny pin prick, if that.
The third is to hope for acceptance but not expect it, to remind ourselves that all of life is a mixed bag. I've noticed that when something bad happens, people say, "Why me?!" but when something good happens seldom are they shocked or do they question why they were so fortunate.
Maybe we were read too many "and they lived happily ever after" fairy tales. For most of us, it takes a good deal of living before we accept that we're not the exception; as unfair as it seem, we will not be spared slings and arrows, and at the end of it all, we'll leave the game the same way that millions before us have left it and the world will go on as before. In that context a rejection shrinks in importance--but an acceptance is still better!
(One thing that makes it easier is to be working alongside others on the same path, and to get support from someone who can give you a constructive outside perspective. Those are on offer via my Writing Breakthrough Strategy Program. It's an 8-week online coaching program also available as a one-to-one process. The next session starts on January 16, 2012. You can find out more here: http://www.writingbreakthroughstrategy.com/)