There's a quote I like from James Clavell's novel Shogun:
“It's a saying they have, that a man has a false heart in his mouth for the world to see, another in his breast to show to his special friends and his family, and the real one, the true one, the secret one, which is never known to anyone except to himself alone, hidden only God knows where.”
The novel implies this was a Japanese saying, which may not be accurate, Clavell probably based it on Jesuit writings from that era. That being said, I like this quote because I think it's applicable to all people, not just the Japanese, especially in this modern age.
Often we are not even limited to three "hearts". Other people can see and bear witness to your life, but they only see a sliver, a fraction of what it is to be you, and only what you choose to let them see. How other people experience you varies for each group. You have your set of high school friends, who know of your early days of hijinks, your work friends who know how you react to stress and how you unwind, your relatives who know how you are during the holidays in the face of family turmoil, and so on. None of them know the real you, not completely.
It can't be helped that the "true" version of each person is known only to that person alone. No one else lives the same life exactly.
Consider myself. I write a lot about what's going on in my life, whether through social media or through this blog. I strive to be open and honest and true in my dealings with other people, and I am almost always willing to offer up my thoughts without filter, if asked. But despite that, the picture I present to the world is still always incomplete. There are things I omit and things I hold back and things I don't like to talk about. It's something I have since learned to respect in other people as well, despite my inquisitive nature: to hold back when they obviously don't want to talk about something.
(Don't worry I haven't secretly committed any heinous crimes.)
I was reminded of this quote only because I was reading some discussion about private content on the internet. In general, if I post something on the internet, I don't expect it to be private, not completely. Otherwise, why post it on the internet at all? Anything on the internet has the chance to be exposed later, one way or another, and we should be careful accordingly. And "on the internet" here isn't even limited to websites and blogs and social media. "Private" communications are a weak point too, as anyone can capture a screenshot anytime. If you want to keep secrets, then don't put them on a network.
Three can keep a secret if two of them are dead.
There's a Black Mirror episode where the personality of a human who passed away is recreated based on his social media postings and what not. Because of the nature of humans, I don't believe this process can ever be 100% accurate. What you will get is a shadow of the original human, an approximation of who he chose to present himself as. His true self will have been forever lost.