When we are young we are like ...

When we are young we are like a flowing river - and then we freeze.
 Kurt Lewin

Quotes from the same author

The history of acceptance of new theories frequently shows the following steps: At first the new idea is treated as pure nonsense, not worth looking at. Then comes a time when a multitude of contradictory objections are raised, such as: the new theory is too fancy, or merely a new terminology; it is not fruitful, or simply wrong. Finally a state is reached when everyone seems to claim that he had always followed this theory. This usually marks the last state before general acceptance.
 Kurt Lewin
A successful individual typically sets his next goal somewhat, but not too much, above his last achievement.
 Kurt Lewin
No research without action, no action without research.
 Kurt Lewin
Social action, just like physical action, is steered by perception.
 Kurt Lewin