It depends on the reasons and motivations for being critical.
Sometimes people criticize because of envy, insecurity, low self esteem, fear, ignorance, revenge and other assorted negative reasons. Usually, they offer no constructive alternatives to what they are critical of. Then its up to the person to dismiss the critics as clueless.
Sometimes people criticize and its actually just giving good (sometimes hard to hear) advice and they make a worthwhile contribution to an issue. Then its up to the person being criticized to consider the advice, for their own good........accept it or disregard it.
I'm pretty strong in both cases. But sometimes people can be intentionally cruel and that fact, not the actual criticism, is what hurts.