Master Marketer (or, so he tells us), Seth Godin, put a piece on his blog today about the downside of dwelling on criticism. I completely agree that you don't want to spend the majority of your time stewing on harsh comments that undermine progress and your sense of self-worth. However, criticism does serve an important purpose: it makes you aware of perceptions and opinions which you do not have.
I think the real trick is to hear the criticism, decide whether or not you can do something about it, and discard those you can't. If you can do something about it, decide whether it's something you can do now, or something that should wait. If it needs to wait, communicate that you will be tackling it in the future.
I'm a product of art school. Some of the most helpful critique I received was negative. It opened my eyes to possibilities I hadn't even thought of yet. Would it have been productive to dwell on the adverse commentary? No. But, it would have been just as counter-productive to ignore it, as well.