Because it is awkward to be whom you’re not. Not only it feels unnatural, the incongruity shows. May be you don’t notice it but others certainly will sooner or later. That’s why actor gets Oscar for convincing acting within the short span of a movie.
Not that we are stuck in a claustrophobic way in real life. But who we are come through loud and clear in what we say and do. It is like our signature. Some calls it a persona. While possible to modify our appearances, expand our knowledge, or act in guises, our character ultimately wins the day.
But, and this is a big but, a prerequisite to be yourself is to Know thyself. This little aphorism is harder than it sounds. For generations, we human have been pursuing this quest. But, each of us is left to discover on our own.
Be that as it may, the truth remains: get grounded with self as best as you can, through means like meditation, reflection, or whatever, and then be yourself. Good, bad, or indifferent, your consistency action inside-and-out beats other alternatives.
Do you agree that to be yourself you have to know thyself first?