A habit is a behaviour created through repetition. So, something which you have repeated many times and therefore has become second nature. Anything that is second nature is something which has created a pathway in the subconscious mind. Learning to drive a car creates habits which are instilled in us, thus the driving from A to B without remembering how we got there. Out conscious mind switched off for a bot and our subconscious took over.
Unwanted habits such as biting our nails, smoking, teeth grinding, thumb sucking, cheek biting etc are all as a result of a coping mechanism developed due to a response to a certain situation. The more we think about the issue the more it is on our mind and the more we are unable to stop the habit.
Hypnotherapy helps to change the unwanted habit through developing new responses to situations which caused the habit. We can’t change what has happened to us but we can change our responses to it.