is authenticity necessarily a manner of being honest to one's self?

Being authentic means being honest, to some extent. Yet even then, things shouldn't get out of hand. Of course, if you are dishonest to yourself, you also tend to lie to others, because you consider such behavoiurs to be normal and part of your daily routine. You can even get to the point where you stupidly forget who you are, and that, to my mind, is totally wrong.

So I don't recommend being dishonest because it will do you no good in life, you'll get caught at some point and things won't be all that fun for you then.

It is best to be truthful because people appreciate that in a person, if they are sane. I am a sincere person and I've only gotten positive feedback about that so far.

Yet, it is self evident that you don't need to be super-honest because then you tend to self-disclose too much and that isn't appreciated either. My mum has told me this a hundred times and I've sort of stopped doing that, but when I was a child I used to tell strangers about the most intimate things that would happen in my faimly.

So it's all about finding the perfect balance between the two extremes. Everybody knows that being balanced, even in the way we interact with other people, makes life much easier and therefore happier.