"The unexamined life is not worth living."

"The world is full of suffering, but it is also full of people who are overcoming their suffering."

"I am sure that the true way to make a life happy is to make it useful."

"Life is either a daring adventure or nothing at all."

"No pessimist ever discovered the secrets of the stars, or sailed to an unchartered land, or opened a new heaven to the human spirit."