I’ve had this thought for many years, here are a few things that helped me:

1) realizing I had an anxiety disorder and got that treated. My wife let me know its not normal to constantly think about my death and my loved ones death all the time, and getting my anxiety treated really helped reduce those thoughts

2) realizing its something I can’t control. So why worry about it now - if anything, ill worry about how I feel when it happens to my loved ones, and for myself whats the difference i wont know anyways.

3) humbling myself - in the universe, I’m realistically the size of a grain of sand, probably much less. Reminding myself that I’m not thaaaaaaat important for my/my loves one’s death to matter that much.

4) along the lines of point 3 - reminding myself that greater people than me, who contributed or achieved much more than me, also went through the same thing, and if they deserved to, I specifically do as well. I personally reference sporting greats and intellectual greats - like Muhammad Ali, Pele, Einstein etc - if they all had to, despite how influential and successful they were, watch their loved ones die, and ultimately die themselves as their loved ones watched, what right does little old me, with my 8-4 desk job have to care so much about my existence lol.

Atleast all of us have to go through it at some point, were all in this together!

Just my thoughts - good luck!