I'm currently training, and getting through my online course, I work with a really difficult dentist too but I think I just need to get through the course, qualify and then you can shop around other practices until you find one that you're comfortable and happy in. You shouldn't let the dentist put you off doing something you want to do. Not all dentists are like that (I've heard) so if you get back into it you may find somewhere that makes you enjoy the job