When I was in high school I was deeply afraid of death and thought about it daily. Then a few times over that period I got sick. Not unusually, or deathly sick, but feeling like utter garbage and perhaps enough to wonder if there was a very remote chance that the illness could threaten my life. And everytime I wondered that I realized that I had no fear of death which struck me as really odd given that I would otherwise feel true terror at the thought of impending doom. This led me to the belief that fear of death is really just a biological impulse, and that pressing that mental button that says death is scary is just... not actually a reflection of your mentality but a biological response which can be dulled by physical circumstances like illness. By recognizing it wasn't really a rationally based thing, it became much easier to just not touch that biological scare button when contemplating death, and now it rarely bothers me (though it's still easy to trigger terror if I want to).

I feel I arrived at a similar place to the author but on a much less romantic path. Not sure if I would have the same experience if the illness actually felt life threatening in an active way (e.g. breathing problems like the author experiences).