It is the pursuit of happiness that thwarts happiness.

A human being is not one thing among others; things determine each other, but man is ultimately self-determining. What he becomes - within the limits of endowment and environment- he has made out of himself. In the concentration camps, for example, in this living laboratory and on this testing ground, we watched and witnessed some of our comrades behave like swine while others behaved like saints. Man has both potentialities within himself; which one is actualized depends on decisions but not on conditions.

Man can only find meaning for his existence in something outside himself.

[Speaking of his experience in a concentration camp:] As we said before, any attempt to restore a man's inner strength in the camp had first to succeed in showing him some future goal...Woe to him who saw no more sense in his life, no aim, no purpose, and therefore no point in carrying on. He was soon lost.

And I quoted from Nietzsche: That which does not kill me, makes me stronger.

The one thing you can’t take away from me is the way I choose to respond to what you do to me. The last of one’s freedoms is to choose ones attitude in any given circumstance.

But my mind clung to my wife's image, imagining it with an uncanny acuteness. I heard her answering me, saw her smile, her frank and encouraging look. Real or not, her look then was more luminous than the sun which was beginning to rise.