I celebrate criticism, I do. I look forward to being told I'm wrong, or that I'm looking at something the wrong way, or that my failure was due to some defect in my cognitive process. Why? Because it allows me to learn; to grow beyond my programming. Alternately, it gives me an opportunity to re-verify my intent, motivation, and procedure through rebuttal. Perhaps once I explain why I think why I do, the other person can either learn something themselves, or better focus on whatever issue I may be experiencing.
Some people, however, seemingly tie criticism to their ego. You criticize some decision they've made, or question their motivation and you're attacking them personally, so they respond by being defensive. I ran across a wonderful, wonderful essay which outlined step-by-step how egocentric people view - and react - to criticism, by someone who was endeavoring to overcome it. Bravo, I say. How many times have I heard that overcoming some personal shortcoming is, "too hard?" What then? Once the author of the above essay was able to overcome his admittedly irrational defensiveness he said, "The positive changes in my life after reversing this habit have been huge."
What's baffling to me are those who want "huge positive changes" without having to work at them. Children, for example generally behave this way, but as they mature, understand the nature of the rewards of effort. I would love to go through life with impunity, but that's not how life works. Even a child can understand cause and effect, and our society is built upon these self-perpetuating principles.
Another essay starts, "Criticism is crucial for personal improvement." Given that personal improvement is essential for fulfillment - the underpinnings of a happy life, I question those who eschew it while maintaining that they're happy. I won't go so far to say its impossible, what with all the different permutations of personality, but it seems very unlikely. Or at least unsustainable.
The first essay discussed how important it was to take personal responsibility for his behavior, the second essay chose to view it as externalizing the criticism in order to "supercharge" growth. Once again, I don't personally care how you strive to not be defensive about everything, only that you do. Strive therefore for continuous improvement - no matter how difficult it may seem - for only then will we be fulfilled, and truly happy. Attitude is everything.