I still don't get it. If the author is scared of possible problems accompanying death, he just needs to make sure he has a ready supply of tranqs. What is it

I still don't get it. If the author is scared of possible problems accompanying death, he just needs to make sure he has a ready supply of tranqs. What is it that scares people, rationally, about death? I think the irrational fears can be countered in various ways.