The study of the conditions for change begins appropriately with an analysis of the conditions for “no change,” that is, for the state of equilibrium. - Kurt Zadek Lewin

A successful individual typically sets his next goal somewhat but not too much above his last achievement. In this way he steadily raises his level of aspiration... The unsuccessful individual on the other hand, tends to show one of two reactions: he sets his goal very low, frequently below his past achievement... or he sets his goals far above his abilities.

Only a few years ago one could observe, at least among German psychologists, a quite pessimistic mood. After the initial successes of experimental psychology in its early stages, it seemed to become clearer and clearer that it would remain impossible for experimental method to press on beyond the psychology of perception and memory to such vital problems as those with which psychoanalysis was concerned. Weighty 'philosophical' and 'methodological' considerations seemed to make such an undertaking a priori impossible.

For any type of social management, It is of great practical importance that levels of quasi-stationary equilibria can be changed in either of two ways: by adding forces in the desired direction, or by diminishing opposing forces.