As an adult you learn that showing your true self can be dangerous in an environment where you don't know who can be trusted. We don't get the allowance of children to be weird or awkward. Others are gunning for us, and looking for any possible weakness. One wrong impression can drastically affect your life. So you curate yourself in a way that keeps your personality for those who can be trusted to accept and understand it, and others may see that as boring until they've been let in. It's just maturity; you have to earn the right to have me let my guard down around you.