Habit can be defined as: an acquired pattern of behavior that often occurs automatically (Wikipedia)
Habits are routines of behavior that are repeated regularly and tend to occur subconsciously. The American Journal of Psychology defines habit as: “A habit, from the standpoint of psychology, is a more or less fixed way of thinking, willing, or feeling acquired through previous repetition of a mental experience.” Habitual behavior often goes unnoticed in persons exhibiting it, because a person does not need to engage in self-analysis when undertaking routine tasks. Habituation is an extremely simple form of learning, in which an organism, after a period of exposure to a stimulus, stops responding to that stimulus in varied manners.
An example of habit formation is the following: If you instinctively reach for a cigarette the moment you wake up in the morning, you have a habit. Old habits are hard to break and new habits are hard to form because the behavioral patterns we repeat are imprinted in our neural pathways.The good news is that it is possible to form new habits.
As behaviors are repeated, there is an incremental increase in the link between the context and the action. This increases the automaticity of the behavior in that context. Features of an automatic behavior are all or some of: efficiency, lack of awareness, unintentionality and uncontrollability.
The use of hypnosis to break habits is extremely successful as the process is directed towards the programming in the unconscious mind. This does not mean that the client is brainwashed but instead the thought process that goes through the unconscious mind to perform the habit is changed.