The best way to explain exactly how hypnotherapy works is to use the above diagram. This concept was developed by Dr. John Kappas as part of modern hypnotherapy. It shows the various components of the mind (not to be confused with the physical brain) and how they relate to each other, as well as the hypnosis and hypnotherapy process.
The Primitive Mind (age 0 - at Birth)
To begin with, assume the large circle is the whole mind. The piece at the bottom is the primitive mind. That is present at birth. We are all born with 2 fears, and 3 responses to those fears. The 2 fears are 1) The fear of falling, and 2) the fear of loud noises. All other fears are learned later. The responses to these stressors are 1) Fight, 2) Flight, or 3) Freeze.
The Subconscious Mind
After this initial set, for the next 8 years, the child develops their subconscious mind by adding in new associations. Some of these are negative, some are positive. And they might be different for different people. For example, one child learns that dogs are friendly and loving, while another learns they are mean and dangerous. They chase and bite. Each grows up with an entirely different set of emotions about dogs.
The subconscious mind is approximately 88% of the entire mind. This is where your emotions come from. Your fears, your anger, your pride, your shame, etc. The known associations drive your emotions, and your emotions drive your behavior, for the most part. This is the most powerful part of your mind, and yet you don't have conscious control over it. That is what hypnotherapy is for. This is the process that gives you that control.
The Conscious Mind
This is approximately 12% of your overall mind. This is where you reside during your waking hours. This is where you do your thinking, analysis, reasoning, logic, etc. Your willpower comes from here. When your conscious mind has decided that it wants something but the subconscious mind wants something else, then the subconscious mind usually wins because it is 88% of the mind, and drives your emotions, and to a large extent, your emotions drive your behavior. Not always, but the willpower is usually outweighed by the emotional drives of the subconscious mind. This is why it is so hard to break a strong addiction. The emotional side wants it more than the logical side wants it to stop.
The goal of hypnotherapy is to bring these two sides of the mind into alignment. Specifically, we add messaging to the subconscious to bring it into alignment with what the conscious mind wants logically and rationally.
The Critical Mind
This is the "Gatekeeper". This acts as a filter during normal beta-wave brain activity / conscious activity. The typical person is confronted with about 60,000 message units of information each day. This filters out thoughts and ideas that are not consistent with the beliefs and emotions in the subconscious based on the known associations it has built during the lifetime so far. In order to add new ideas into the subconscious mind, it is necessary to put the client into the hypnotic trance. This gently nudges the critical mind aside.
The Hypnosis Tunnel
This is the conduit that hypnosis opens up in order to send messages into the subconscious. Basically, the conscious mind and critical mind are gently nudged aside to allow passage for new "Message Units" to come into the subconscious and be seeded as post-hypnotic suggestions.
Hypnotherapeutic Message Units
These are the actual post-hypnotic messages themselves. These are positive messages that reinforce the behaviors that the conscious mind wants to have. From stopping fingernail biting, to stopping smoking, or being on time for things, or erasing fears of flying, doctors, dentists, or the anxiety of taking exams, or public speaking. Once there is enough of these messages in the subconscious, the client no longer wants to do the activity they would like to avoid. It fundamentally changes the motivation structure. At that point, the subconscious is now in alignment with the conscious mind.