Haziness means vagueness or cloudiness. When something is hazy, its not clear, you cannot properly see it or define it. As long as something is hazy it escapes characterization and labeling, we cannot do it because we cannot be sure what we are looking at, it may be one thing it may be another, it may have some qualities it may not have them, this is a great comfort if you know what I mean.
"Hell is other people", the famous phrase by the philosopher Sartre, describes the fact that when we are living among other people we are constantly being watched and judged by them. They look at us, sometimes just the face, sometimes words and often actions, mostly in fragments. They create opinions and judgements about us and label as being one thing or another, consequently making us become something or stop being what we are. Judging by itself is not a bad thing and in life people have to judge one another as a lot of things depend on it, for example when being judged in a interview for a job or in the court of law for innocence. Also, the same ability of people produces empathy which is quite desirable. But judgements that Sartre is talking about is made on the whims and feelings of people, driven more by who they are themselves then what it is, not always noble and not always their own. People do it for convenience and they don't burden themselves with "objectivity". In science an effort is made to teach the scientists how to look at things objectively, yet objectivity as a general trait in life is often not shown by scientists and non-scientists alike. When you are living under people's judgements, you are living in Sartre's hell.
People judge when they "feel" confident that they can make a judgement about you and they don't see anything surprising and out of phase with their assessments. There are two ways to subvert people's judgements, one is to actually be different from who they think you are and do something that surprises them and undermines all their assumptions, another is to haze it out. Even if they don't call it the same, people feel Sartre's hell and instinctively try to avoid it. It takes a good degree of deception and sometimes outright lying to convince people that they are mistaken in their assessment. Since this ability evolves out of an instinctive need and takes a long time to develop, it does not feel that bad inside and people can often live with it easily. Whether other people can prove it or not, they can often arrive at correct assessments about us as many of our motives and actions arise from similar needs and experiences as theirs. People just want to protect themselves from the judgements that make them look bad or less than others. Haziness strategy works quite well here, especially for the people who are either unable to change that particular thing about themselves or simply unwilling.
Sartre's hell, compels people to change themselves either to conform to the opinions of other people or to resist it. In both cases, they stop being who they were or whatever they were doing with their life and start being or doing things they had no need for. Sartre was a strong believer in people's freedom to do what they wanted and be what they wanted, hence this is the worst thing people can do to each other. Yet the fact remains that we cannot be everything we want, it may be an ideal to cherish but it wont be the code life runs by. A lot of things are predetermined by first our environment, both the physical and the social created by people, second by who we really are as an individual and that is something we may need to make peace with.
You cannot fly because you are not a bird, but you can always invent a plane. Similarly we cannot be everything we want and do everything we want, though we can reconcile with our limitations and overcome them. It does not sound as exhilarating as 'go and be everything you want' but it does give you a pragmatic route to realizing your full potential. This brings us back to haziness. Now haziness is from Sartre's hell. The haziness strategy is taken by people to protect themselves from the evil judgements but in fact they are going deeper in to Sartre's hell. Not every judgement people pass about you is wrong, though it does tell you something about yourself that you don't see which could lead you to understand yourself better. Also, not every judgement people pass is correct as people are biased and drunk on their own selves, yet that is not enough reason to become defensive and lose yourself. Be whoever you are, learn from whatever comes, do what needs to be done and become what you want.