Not sure it’s helpful, but what cured me of death anxiety was losing a lot of people in my circle in quick succession, a few years ago. 3 close family, 2 friends and 2 acquaintances/neighbours. Across 18 months. Some I cared for actively as they were dying, some I only attended funerals.
The shock began to wear off after the 3rd one. I went a bit numb, and started to recognise the signs of grief before they hit me. Managed quite well. Since then, I’m just grateful when a week passes and no one dies or gets a horrible diagnosis. Especially family. Sounds depressing perhaps, but I’ve found it quite freeing.
I think that people who involve themselves in ‘death’ through work, research, personal experience and spirituality tend not to be very anxious about it. Make peace with it, and although it follows you, it doesn’t punctuate your day in a stressful way. If it starts to interfere with daily life, then go and talk to someone. There’ll be a strategy out there that helps you.
Perhaps also have a think about the downside of immortality, if it was offered to you. I spend a lot of time with really elderly people (like, mid/late 90’s) and they seem to largely have a healthy view of death. I suspect that as your life becomes more limited (mobility, mental acuity, sight & hearing) the decline towards ‘no longer existing’ feels more natural and less scary. It’s as natural as birth, after all.
I hope you find a way to make friends with it.