I think defensiveness may have its roots in insecurity. As artists, we are all insecure, but I can't think of a better way to get secure in your craft than to listen to others constructive criticisms and do a lot of research on your chosen craft. The criticism is not about YOU, it's about your art. It's hard not to take it personally because art is a part of us; like a child we have given birth to. We need to hear how beautiful and wonderful it is. Rising above that will open up a whole new world of supportive friends and inspiration enough to make you soar. It will also build a professional attitude within yourself, as I don't know a client that doesn't want to change something about your wonderful creation. If you work with the client and maintain a non defensive attitude, the whole experience will be a pleasant one and one in which you may have a new client for years to come. I have been drawing and designing my whole life, and I feel the more I learn, the more I realize there's even more to learn. It never ends and that's what exciting about it. Drop the defensive walls and open your art up to new possibilities. Explore taking your art to that next level of being the best you can be.