If you want to understand the jungle, you can't be content just to sail back and forth near the shore. You've got to get into it, no matter how strange and frightening it might seem.

It is in applied psychology, if anywhere, that today we should be modest and grant validity to a number of apparently contradictory opinions; for we are still far from having anything like a thorough knowledge of the human psyche, that most challenging field of scientific enquiry. For the present we have merely more or less plausible opinions that defy reconciliation.

A man who has not passed through the inferno of his passions has never overcome them. They then dwell in the house next door, and at any moment a flame may dart out and set fire to his own house. Whenever we give up, leave behind, and forget too much, there is always the danger that the things we have neglected will return with added force.

Life is teleology par excellence; it is the intrinsic striving towards a goal, and the living organism is a system of directed aims which seek to fulfill themselves.

New ideas are not only the enemies of old ones; they also appear often in an extremely unacceptable form.

You are what you do, not what you say you'll do.

Everyone can afford to give away a smile.