Once a thought is repeated, it strengthens a pattern; The stronger the pattern the quicker it becomes a belief; Once a belief, it exerts a powerful influence over your judgements, behaviours and experiences, often unconsciously. It is in effect self fulfilling. So achieving a mental 'balance' through hypnotherapeutic techniques will not only harmonize your electro-chemical activity in your brain, but increase your ability to use your imagination , your intuition, and your creativity to change beliefs and see different perspectives.
The subconscious mind is never right or wrong. It merely acts on what it 'knows' or has learned. It doesn't 'reason'. It will quite happily grind out falsehoods as it will truth. Hypnotherapy helps 'bypass' those protective mechanisms designed to protect our beliefs.
Sometimes these powerful learnings are not for our own good. For example, someone may have been told, as a child, that they were clumsy and accident prone. Once that suggestion becomes a belief — perhaps through repetition — that belief exerts a powerful influence on all their future performance, so hypnotherapy is possibly one of the most important practices to learn. It is a truism that when you change your usual patterns of thinking you will inevitably change your reality.