Every day that we are alive a new tiny piece of the puzzle regarding the mystery that is you emerges. The combination of life experience and reflecting leads us to some new morcel of insight.
If you are older you have hopefully stopped mostly caring about what others think and have plunged into your own psyche to discover who you are; perhaps who you've always been but were afraid to be.
People will believe who you tell them you are the caveat being that you need to believe it too. There is no fooling the self because that would be pointless and blatantly transparent.
I see people asking questions publicly like "am I this? how do I know I am that?"
If we are asking someone else we've missed the point have we not?
If you don't know they most certainly won't know either.
