I have several times told my wife (and she does not understand) that I do not fear death. I fear dying. The result can be anticipated with joy, but the transition is full of uncertainty.
I liken it to the various surgeries I have had (thyroid removal, artery catherization, heart bypass, bladder removal. There was pain, sometimes considerable with each of these. Pain is often temporary though I am well aware that some experience pain everyday.
Each time I was put under, I contemplated not waking up and that held little fear. But I also several times knew that my life was changing and I would never physically be what I was, but each of these things also provided considerable if not eternal health benefits.