I hope this is the right sub! As a young adult I did something very childish. I used to send myself hate mail on Tumblr as a way to just stand up and show others I could defend myself. I also did it sometimes when I felt like I could express how I felt so I did it that way. It was very stupid and childish and I regret it. But one time I did something bad. I sent MYSELF anon hate about my SO. I said how they were a bit toxic and didn't love me. The only reason I did this was to have an excuse to defend them and prove to them that I would always defend them no matter what anyone said. I wrote a long reply to 'myself' back defending my SO. This was all a very dumb way to go about things and I realize that. But I can't seem to forgive myself. My so thinks it was a stranger but it was me who did it that one time. (I also should add I used to send asks about them saying how great they were too so I had an excuse to agree and such) but the one bad one I feel a lot of regret for. I told my SO I didn't know who it was but I did.

TLDR; Is this just a silly childish mistake or something relationship ending bad? Is it something so bad I am horrible if I never tell?

I feel terrible and the guilt for this is so bad I actually want to die. I love them so much but I feel like I hurt them so bad in the same way cheaters do.