This kinda shit happens every day. I used to complain that every day felt the same and then May 9th came, and now every day IS the same. Ugh, same wake-up scream, same machete-wielding asshole, same everything, with slight variations. One thing that never changes... is I die every single day. I die.
The old wheel turns, and the same spoke comes up. It's all been done before, and will be again.
Basically what we do in life I is reduced to subconscious routines.
You've seen one post-apocalyptic city, you've seen them all.
You follow in the tradition that you're handed.
All authors are inspired by something someone wrote before them. The first rule for a great novelist is to copy.