Much of the faultfinding is motivated by jealousy. Some people try to lift themselves up by putting others down. If they can’t be successful they aren't going to let anyone else be either. We should simply ignore them. Don’t give those critics the tribute of our resentment.
Others however, may oppose us and our ideas because they do not agree. We should deal with these critics differently. If they aren't mean spirited about their opposition then we can do ourselves a favor and hear them out. I have found that sometimes my critics are at least partially right. If we are wise we will allow our critics to sharpen us and improve our ideas.