It’s because you have a conscious mind (all of the thoughts, memories and feelings of which you are aware at any given moment) and a subconscious mind (all of the thoughts, memories, feelings and urges, and of which you are largely unaware).
And sometimes they don’t agree about what is best for you. Your conscious mind may want to change but according to your subconscious mind there is some good reason to keep the unhelpful behaviour or way of being.
Your subconscious mind is responsible for 90-95% of your brain’s processing power, which leaves only 5-10% left for your conscious brain to do all that is required of it (critical thinking, planning, executing, problem solving, talking, working, reading, etc).
Given that the power of your subconscious mind is massively more than your conscious mind, if it isn’t comfortable or really on board with the change you want to make, then change will be incredibly difficult to achieve.
So, for change to occur you need to build positive associations to the new behaviour (or way of being) on a subconscious level.
Hypnosis is a safe and effective way to do exactly that.
Hypnosis takes you into a deeply meditative, relaxed state in which you can sidestep the conscious mind and gain access to your subconscious mind. During hypnosis the conscious mind relaxes deeply enabling the subconscious mind to become more receptive and open to change.