I am about 10 months in to a similar experience, pre-diagnosis, and I can echo your statements about how terrifying the unknown can be. Being surprised to wake up in the morning can really alter your perception of reality. I think there is an enormous amount of abstraction needed in this perception to avoid going insane. I think it is important to be able to remove oneself from the reality of ones own mortality and I don't think it is possible to live normally while being too aware of it. Having said that, If recover from this whole thing I think it would ultimately be a good thing to have gone through as my appreciation of normal life would be much higher.

Good luck for your surgery.