There is nothing everyone is so afraid of as being told how vastly much he is capable of. You are capable of - do you want to know? - you are capable of living in poverty; you are capable of standing almost any kind of maltreatment, abuse, etc. But you do not wish to know about it, isn't that so? You would be furious with him who told you so, and only call that person your friend who bolsters you in saying: 'No, this I cannot bear, this is beyond my strength, etc.
Søren Kierkegaard, from the journals
To my mind, this quote is up there with any of his aphorisms (including this), except for that amazing quote that begins pretty much every Kierkegaard journal or quote compilation:
I have just now come from a party where I was its life and soul; witticisms streamed from my lips, everyone laughed and admired me, but I went away — yes, the dash should be as long as the radius of the earth's orbit ——————————— and wanted to shoot myself.