High self esteem is incorrectly seen as something you should strive for, when in reality there is nothing good about high self esteem. High self esteem is usually inflated and does not reflect who you are as a person.
People with overly high opinions of themselves under appreciate others' worth because they believe they are better than everyone. On a personal level, this could lead to isolation and for others, you are probably not very well liked. People who are cocky and full of themselves as seen as less attractive and desirable. If you love yourself too much, you'll find that unfortunately, you are the only one.
Often times undeserved praise can be the cause of such inflated self esteem. Parents can be too kind with their kids and end up making them really narcissistic and self involved. This occurs in development in programs that reward natural intelligence. Gifted programs, while useful and worthwhile, can have the negative effect on some children of making them feel like they are better than other kids. Some children might not work as hard in life because their sense of superiority makes them feel like they don't have to. Similarly if you have parents who constantly praise you for mediocre to bad work, you can develop high self esteem.
Another cause of high self esteem is quite the opposite. If people constantly put you down, you tend to overcompensate by inflating your sense of self. This is one of the best explanations of why high self esteem is a problem. High self esteem in pure form is actually rare. More often than not, high self esteem is just a mask for inner insecurities. Being told all your life that you are stupid, can make you overcompensate by feeling and acting cocky about your looks. This the worst kind of self esteem problem because deep down you actually have low self esteem.
Both of these types of high self esteem can lead to problems in decision making and social relationships. Your friendships will suffer if you exude an air of superiority when you interact with others. People are very worried about their flaws, but in reality it's your flaws, not your good qualities that make you endearing to others. Often it makes you relatable, and it lets people know that you have a realistic sense of worth. People like others who can admit to their flaws. It is a sign of maturity and confidence because only truly confident people will be open with others about their flaws. That is the fool proof way to tell if someone's self esteem is high or whether it is good and realistic but not over inflated. If someone can only talk about the good traits they possess, their self esteem is too high. Someone who can be frank about both their strengths and weaknesses has truly achieved a good level of self esteem.
That is why we find humble celebrities more approachable and likable. It is easy to see instances of unearned high self esteem in those that are constantly in the limelight. The late Marlon Brando, was undoubtedly an excellent actor but his high self esteem made him a notoriously rude and standoffish individual. He had a reputation for ignoring fans requests for autographs and pictures to even being downright mean to those who asked. Situations like that make it clear that while it is understandable why some people are famous, that does not justify being so overly pompous.
In history, you can also plainly see how all the ways that high self esteem can develop and how it can go wrong. Hitler, for example, was a meek young man who was not appreciated and who was by many standards a failure. He grew up to have such an inflated self esteem, that his hateful propaganda created one of the worst human rights atrocities of all time. He became hateful and grew to be a tyrannical monster. His desire for greatness stemmed from his need to overcompensate for what had all his life been extremely low self esteem.
These examples illustrate why high self esteem is just as dangerous if not more so than low self esteem. It is problem that should be looked at and changed for the benefit of yourself and those around you.