This is because it's possible you were. We have several layers of 'mind'. For our purposes there are only 3 that we need to be interested in. This is going to be an oversimplification (so I don't get bombarded with criticism from neurologists & psychologists, but a good working model). The part of the mind we're most aware of is the conscious mind. With this part we do our reasoning, make decisions, and plan & do things. This is where we have our 'willpower', and some people believe that this is the only part of the mind there is.
There must be another part that's fighting our wishes, or we wouldn't carry on doing some things we don't want to do, like smoke, carry out rituals such as in OCD, do drink or drugs to excess, or feel bad (or good) for no apparent reason.
We are victims or benefactors of our programming. Like a computer that we either load with a good operating system, or a bad one (like some versions of W*nd*ws), our ability to have a happy & fully functioning balanced life depends entirely on what we and other people have programmed the part of our minds that's known as the subconscious, in the past. If you doubt the existence of that part of the mind, whether it's a physically separate part of the brain or not, then next time you talk to someone, justnotice what your hands are doing. Most people make hand movements to emphasise what they say without any conscious direction. If there is only the conscious mind then where is that coming from? This is only one tiny example but you get the idea. More to come on this.
This means that it's a fast & direct way to get at the 'works', and start to make changes in a subtle (or sometimes very dramatic) way. It's like replacing a faulty program in a computer with a better one. People find that they aren't battling with themselves any more, they stop self-sabotaging. The start to like themselves more. The way hypnosis works is to quieten down the 'critical factor', part of the mind that can get in the way when you want to change your ideas or habits, when it's normally saying "nope, that's the way I've always done it, and if it was good enough for my dad/mum/teacher/friends etc then it's good enough for me". It can be got to sit & watch quietly as the desired changes are brought about. The client has to want these changes at a conscious level.
We don't have access to the critical factor normally, it makes it's own decisions about what's accepted into the deeper parts. Once it's been bypassed with a trance state then it'll be 'updated' with the change of behaviours that we've slipped past it which then feed back to this part so it looks out for and accepts similar ideas in the future, building on the good work that we start here. More to come on this.