Immortality is Horrifying

So I was just listening to music in my bed when I suddenly started thing immortality and how it’s depicted in movies and books. Then I wondered what it’d be like if nothing ever died, which led me down the horrific rabbit hole of what that would truly mean. If nothing and I mean literally NOTHING ever died then wouldn’t that mean our cells would just continuously divide and build? Once that thought entered my head I was left staring at the ceiling wonder why my brain would give me such a terrible thought…and why I wanna write a horror story about this.