I wasn't really afraid of the dentist as a child, and I never understood why my first ever real panic attack out of the blue occurred in a dentists chair. Since than I am severely scared of the dentist. 

Tomorrow I am having an appointment which is long overdue, I really need to go since I have really bad situation with one tooth that even started giving me severe pain (the tooth might even need to be pulled). I have been treating this one tooth almost a year because of my fear ( I am constantly canceling appointments). I have so many possible scenarios in my head as of what could go wrong, some (most) of them irrational and some of them more rational. I don't want to write all of the scenarios and fears that I have in my mind for possible triggers, but please I need some advices and techniques for how to calm myself and get done with and fix this tooth once and for all.