There is a courage of happiness as well as a courage of sorrow.

More important than innate disposition, objective experience, and environment is the subjective evaluation of these. Furthermore, this evaluation stands in a certain, often strange, relation to reality.

In the investigation of a neurotic style of life, we must always suspect an opponent, and note who suffers most because of the patient's condition. Usually this is a member of the family.

It is from among such individuals that all human failures spring.

Each generation has its few great mathematicians, and mathematics would not even notice the absence of the others. They are useful as teachers, and their research harms no one, but it is of no importance at all. A mathematician is great or he is nothing.

The feeling of inferiority rules the mental life and can be clearly recognized in the sense of incompleteness and unfulfillment, and in the uninterrupted struggle both of individuals and humanity.

The only worthwhile achievements of man are those which are socially useful.