Just to provide a balance...
Hypnobirthing is great, but it's important to recognise it's limitations. The amount of pain you're in during birth isn't really dictated by how calm you are - being calm certainly helps but the actual difficulty of the birth is dictated by:
Position of the baby on the day, plus
Your physiology (pelvic shape etc.)
Some births are just going to be more painful than others - there's no hard and fast rule that applies to every single one (some back to backs are agonising, some ok.) it's the interaction between your anatomy and foetal position that dictate length of Labour/pain levels.
So... why am I saying this? Basically because it's important you don't think that if you train then need intervention you've failed. Hypnobirthing is fantastic for straightforward births, for staying calm, for staying centrered. But some births, from the start, are going to need intervention. It's really important that you don't buy into this 'you can breathe any baby out if you're calm' myth.
Certainly do the course, it's a useful skill, but stay flexible with your expectations- birth is inherently unpredictable. I hope yours goes smoothly