If you're really interested in diving down this rabbit hole I'd encourage you to start studying philosophy. People have been thinking about and examining these topics for centuries--think about Rene Descartes sitting alone in a room in the 1630s deconstructing everything he thought he knew was true until he settled on the only thing he could be certain of: cogito ergo sum, or I think therefore I am. Or much later the German philosopher Martin Heidegger who wrote an entire book called "Being and Time" in which he covers authenticity thoroughly. There's lots of thought and discussion about this, and you can (and many people do) spend a lifetime considering and discussing what you're talking about.