That's a pretty naïve view, IMO. A person isn't composed of just one personality. You're a different person in different places and situations, and it's uncomfortable to mix all of these personalities into one.
No, I am always the same person in any situation. A mature person is comfortable with who he or she is, and accepts all facets of his or her personality. If you are not comfortable with something about yourself, perhaps you need to examine why.