Emotional equilibrium is a state of stable balance, such that any disturbance from outside tends to be corrected.
Let’s assume that everyone has an internal ‘regulating machine’ that requires ‘resetting’ after an upsetting event, but the great majority return to emotional equilibrium within days (that is, they have a ‘normal’ depressed mood state). Some people, however, are unable to reset their mechanism easily, thus losing their ‘emotional equilibrium’. They remain essentially ‘stuck’. Their personality styles and ways of dealing with events ‘sustain’ the depression, rather than enabling them to ‘get over it’.
So how can equilibrium be lost? There are two main ways:
1. The machinery can fail; for example, if the keel on a yacht breaks off, the yacht will capsize.
2. A ‘positive feedback loop’ can develop. This means that two or more factors can influence each other to such a degree that a small disturbance leads to a further disturbance. This loop is sometimes also called a ‘vicious circle’. An example of feedback occurs when a microphone is put too close to a speaker. A small noise from the speaker is amplified into the mike, and further amplified by the speaker. While the feedback loop can be of use to create musical effects, such reverberation (mulling over and rumination) is not useful for humans.