Psychology

An emotion can be defined as a feeling that involves thought, changes of the physiology and an apparent expression or conduct.

Theories of Emotions

The James-Lange theory
This theory was suggested by William James and Carl Lange thus the James-Lange theory. It theory suggests that when an alarming event occurs, it first arouses the physiology and then we later interpret the arousal. Only after that do we experience emotion. Therefore emotion isnt experienced when the arousal has not been registered based on the occurrence of an event.

Event                Arousal               Interpretation             Emotion

Facial Feedback Theory
In this theory, emotions are described as the change of facial muscles. Hence when one smiles, it means that he is experiencing joy or pleasure and also when one is frowning then he is experiencing grief. Therefore when our facial muscle changes, this is indicated to the brain which as a result provides the source of the emotions.

Event                  Facial changes                 Emotion

Conclusion
In order to for one to take certain actions, one has to be motivated by emotions which also provide a certain force that enables the direction and sustention of behavior.