Here was my thought process with coming up with the story:
"Wouldn't it be cool if you could go back in time, just to mess with your past self to see what would happen? Or maybe you could help your past self do something you never got a chance to do. Maybe win the lottery, or become a rockstar or something. Or maybe there's a person that your past self always wanted to be with, and maybe you could help. But what if you still wanted to be with that person too? Then maybe you'd become jealous, and bad shit would ensue. Maybe you from the future is evil, and the story could be told from the perspective of you from the past..."
It practically wrote itself past that point.