We often see something we like, and we want it. The same situation is with our personality. We want to be someone else. This starts very soon. For example, in high school, you can see many girls who want to be as the most popular girls in school. Also, boys want to be as the most popular boy at school. These were just two, most basic examples. There are a million more.
Why we want to be someone else is simple. We think that their life is perfect, and we want to have the same. Actually, when you look at someone’s life, you only see half of a story. You can see that person, in that particular moment, not more. So, you may assume that he/she is happy and has a perfect life, but it doesn’t have to be true. This also applies to the Facebook comparison (when you compare your life with the lives of other people on Facebook).
The real question is, why you want to change yourself? Why you want to be like someone else. You have your personality, your desires and your goals. Many people like you for that. If you change them, you will be a copy of some person. If you want to be a unique, you must have your own personality. Other people will respect you for that.
You cannot change yourself because, your personality is deep in your brain. You can try, and you can fool people around you. But, at the end of a day, you will be the same person as before. So, don’t try to change yourself, it is impossible.