I am a hypnotherapist myself but was very sceptical when I began the course. I think some people naturally find hypnosis amazing for many things, and some don't. I would not consider myself a 'natural' for being hypnotized, however I have seen some really amazing results with my clinic. I also had to practise a lot during my 2 year training, and focused on my increasing phobia of wasps in a one-off practice session. I literally went overnight from being terrified and hysterical if a wasp came near me, to not being bothered at all by wasps or bees. Even more interesting to me is that I was just 'practising' the phobia replacement technique with a colleague and we interrupted ourselves frequently to discuss the scripts, etc. So I really didn't expect it to actually have any effect on my phobia, but it has.
I think the best chance of success with hypnosis is a very high motivation level (you really want change) and an open mind. I can truly say, even as a hypnotherapist myself, that hypnosis has changed my life dramatically and had a really positive effect in lots of areas, stress management, sleep, etc.