I'm looking for a short story where the main character figures out he has the power to 'save and reload' his life to try out different scenarios. He pretty quickly becomes kind of a monster in the saved version, being violent and aggressive to the people in his life. The story ends with him realizing that he's not erasing the 'unsaved' parts of his life, but spawning off different timelines where the things he did have consequences. Near the end, he interacts with a 'him' (or maybe someone important to him) that gets into his timeline.
I know I read this in the last 3-4 years and am fairly certain it was online. It may have been a response to a Reddit writing prompt or something along those lines.