Our behavior reflects what we have been transformed into.Throughout our lives, we will be in different circumstances and accordingly, we develop ourselves into a different set of personality.
Personality is a trait of any individual defined in the way we behave or react to something. So, when we all were still small, we believed in almost anything. Then, with the time, our interpretation kept on changing. In the literary sense, we call this maturity. Then we come to know that certain things we had been told of were not true. Now we have defined a set of rules and principles and our decisions will be based on those. This has been the fact with each one of us that we continue to learn new things and we adapt to certain conditions which remains different to different people and will keep on adding to our experiences and expertise.
This could also be the basis that adds to the beauty of this world that we don't find anyone exactly like us.