A state is a combination of an internal representation and the internal kinaesthetic feeling that goes with it, and we describe this state with a label such as ‘alert’, ‘sleepy’, ‘sad’, ‘cheerful’, ‘depressed’, ‘happy’.
Remember that it is a combination of the internal representation and the person’s physiology that results in a certain state. The state you are in can affect your physiology and therefore your behaviour.
Your internal representation creates the state you are in and the state leads to the behaviour or physiology. Changing your physiology will also result in a change of state. Being in control of your state means you are in control of your body and mind, and therefore your results.
See also the NLP Communication model, What is NLP?