It could be delivered by mail, email, by hand, or even by pigeon.
It is sometimes short, sometimes lengthy, and with deep, profound, or simple feelings.
What is it?
I never was, am always to be,
No one ever saw me, nor ever will,
And yet I am the confidence of all,
To live and breathe on this terrestrial ball.
What am I?
I am the reason you run, because I allow it. I am the reason you scream. I am the cause of all your pain. I am a cage from which you will never be free.