If you're engaged in as many different types of relationships as me, you need to be able to be flexible, adapt to the particular type of people you are at that point engaged with. Then, which "self" is the real self? There is no one singular self. The self is the composite aggregation of all of these differing selves. Authenticity to oneself becomes moot when all of these differing selves or roles are you. Playing the role, acting the role--you become the role. Acting is living, as long as the actor and audience both believe the performance.
We are constantly acting. There is nothing new about this modern age where we seem to have multiple roles, multiple identities. The reason why it's obvious that we're acting in many different roles now is that the need for many different roles didn't exist before. In a pre-modern age where you only saw your family on a farm for most of your life only required one singular identity. And only with the invention of language and print, where you could formulate your own thoughts, did a conception of an individual self become possible. But with industrialization came modernity. Urbanization, transportation and communications revolutions that enabled one to meet and interact with many more people required one to have multiple identities--co-workers, friends, family, relatives, acquaintances, etc. Now with the Internet and with continued globalization, the opportunity to expand our networks grew exponentially and the need for multiple, often disparate identities.
I once thought that I needed to be true to myself when interacting with different types of people. Don't deceive. Don't say something you are not. Don't say you're Christian when you're not Christian. But why? When we're all performing, acting a role, what importance does authenticity to one's self have? Only when the performance is no longer credible must the show stop. But before then, play on and reap the benefits. Fake it till you make it.
All the world's a stage,
And all the men and women merely players;
They have their exits and their entrances;
And one man in his time plays many parts...
- William Shakesphere