There certainly is a "too little". I've met people that use the mindset of "I don't care what people think of me" as an excuse to act like assholes. But there is also "too much" because I don't think a person should compromise their core values to please people around them. I find the phrase " you care too much about what people think" is most often used when people hold back and don't live up to their full potential because of fear of a certain judgment. But the same is true in the opposite case that you can pass up on opportunities because you don't value other people's opinion. LIke in most cases, there is a balance to be found. I find that for different people, lifestyles and career the threshold of "caring too much" is different. And there is a distinction to be made about who the "people" are. Some people's opinions matter, some don't.