That's cool that you write original fiction! Fanfic is probably great practice for that, but original fiction comes with its own challenges as far as creating purely original characters and developing the relationships between them from scratch. I haven't branched out into original fiction, but I have written AU, which is a nice in-between.
I feel you on the guilt thing, Mare. I've mostly gotten over that after years of torturing the Boys in my stories, but sometimes I still write stuff that makes me question why I spend my free time this way and worry about how they would react if they ever read it. I'm sure that is freeing to move from writing about real people to fictional characters.