Hello! This is my first post in this forum, so bear with me if it sucks!

So, the fact of my mortality hit me like a bloody truck in April of this year, when I went to deliver my great-grandpa his newspaper and some essential shopping items (my mum was his primary carer since her dad/one of his sons died when she was 3 and his other two children didn't care for him at all) since my mum was at work and the door opened to his neighbour, who told me that he was dying. He was 91, so he was going just of natural causes, but I decided to be there with him when he died so that he wasn't alone. I didn't tell my mum until that evening, and she was devastated, not so much of his death, more so that I was there to see it, even though he went completely peacefully. She'd already endured the losses of both of her parents, since her mum died in 2011.

That night, though, all I could think about was that this was going to be me one day in my deathbed. I'm so privileged that I got to have a relationship with my great grandfather, and that my dad's parents are both still alive, but it makes the fear that much more real. I turned 19 this May (on the 19th ironically) and I didn't even enjoy it, because my mindset was trying to process the fact that I'm getting older and becoming an adult, and this mortality shock has made that so scary to me!
I'm also doing my exams to get into university at the moment, so my stress is through the roof, but this fear has spiraled out of control for me - first it was my mortality, then I was thinking about how my parents are going to die someday, as well as my auntie and my grandparents. I have an especially good relationship with my grandfather, and he's 74, so not getting any younger. Even when I see my friends at college, I imagine us all in our later years and how some of us will have likely died by then. Me, my mum and my auntie are all very close in age as well, since my mum had me at 17 and my aunt was 15 at the time, so they are now 36 and 34, and I feel so guilty that I've been crying about my nanna's death, when they lost their mum at 29 and 27 after never really knowing their dad. I couldn't imagine losing my mum and dad, I love them so much, but it makes me feel so guilty inside because I know there are so many people out there worse off than me.

Essentially, I just want some advice so that I can kick these thoughts out of my head for good and just get on with my life. I wanna enjoy my last year as a teen as much as possible, and I want to go back to when I just didn't think about this stuff.

With thanks x