This paradox is named after Admiral Jim Stockdale who was the highest ranking US military officer imprisoned in Vietnam. He was held in the Hanoi Hilton and repeatedly tortured over eight years. The "paradox" lies in the way that he managed to survive where others perished.
"I never lost faith in the end of the story. I never doubted not only that I would get out, but also that I would prevail in the end and turn the experience into the defining event of my life, which, in retrospect, I would not trade."
Asked: "Who didn't make it out?"
"The optimists. They were the ones who said we're going to be out by Christmas. And, Christmas would come and Christmas would go. Then they'd say, We're going to be out by Easter. And Easter would come, and Easter would go. And then Thanksgiving, and then it would be Christmas again. Then they died of a broken heart.
"You must never confuse faith that you will prevail in the end - which you can never afford to lose - with the discipline to confront the most brutal facts of your current reality, whatever they might be."