I don't often write in first-person. Many of my early stories (short Lovecraftian-ripoffs) were written as such, but I actually thought of myself as a man writing them so I didn't really risk putting too much of ME into the stories. My published novella "A Touch of Scarlet" is written in first-person, and there is a bit of me in the character of Scout, but the story is so "out there", it was easy to make the separation.
PINS is different.
A lot of events that happen in PINS are based on actual events. A lot has been skewed for the story's sake because, well, I never worked at a strip club/ bowling alley named PINS. Nor have I witnessed several gruesome murders. Still, as I wrote PINS, I realized that the main character, Eva "Birdie" Finch, was starting to turn out a lot like me. There's a fine art to putting yourself into characters without turning the character into YOU, and I noticed the line was starting to blur.
So what did I do? I committed suicide....in a way. After I was conscious of my error, I definitely started making Birdie's personality different from mine, but I still wasn't satisfied. So, to put an end to my Mary Sue-ing once and for all, I created a character that represented ME. I threw in a nickname "Cherry" and some of my famous McHugh color, and then, I killed her off. The section of the story needed a death anyway, so why not slaughter myself? It was rather fun, actually.
Since then, I have had no problem differentiating Birdie from Jessica. I'm me and she's her, and poor little Cherry is sliced to bits on the floor of a strip club shower room.
Suicide for the story. It was an approach I'd never tried before, but amazingly, it worked like a cadaverous charm.