Along with Hops' excellent suggestions, one thing that helped me to crack the auto-functioning "conditioning" to engage in self-harm, and still helps... is to let yourself chew over some really radical "ideas". Plant the idea and see how it organically spreads throughout yourself, and helps to change the "landscape" of the same old - same old.
My buttons were so sensitive to "mom" pressure that all I had to do was think of something she'd said, and it would set me off.
So: one idea that helped a great deal was to always call her by her name, in my thoughts about her. The idea being, that she is a human being... separate from me... as I am from her... and to recognize my own unique adulthood - capable, competent, creative, etc. That was who I was OUTSIDE of my relationship with mom. It made no sense that this one relationship was the reverse. At a subconscious level, this idea is a way to declare to the world (and most importantly myself) that "mom" doesn't have any power over me - at all; I am the one driving this "me" person... steering... choosing... setting the temp controls and radio station frequency.
Over time - and you can't expect instant results - I began understanding what a pathetic person my mom was... all those rediculous games, boundary intrusions, etc. were some feeble, desperate, sneaky way to try to feel better about herself -- at my expense. But I also started to see at the same time... that I'd had the "power" to choose how I reacted to her and her crap all these years. I indulged in some self-rear-kicking about that... but it's really pointless; I could "redeem" myself with myself now, by being a person who wasn't taken in, conditioned to jump as high as ordered, and kowtow till I melded with the floor and let her walk all over me. Oh - and a side effect of planting this idea was that I didn't feel anywhere close to the old level of guilt about it, either. (That by itself felt tremendously liberating!) That idea is still flowering and spreading and helping me heal in ways I am only barely conscious of.
This idea helps whether you're NC, LC, or still dealing with her... it's kinda like a "get out of jail free" card and is explicit permission to grow beyond the confines of the prison-like relationship your mom still thinks exists... of her power over you. Sure, outwardly you may very well decide to stay engaged in the same crap with her... but inwardly, the threat-level decreases, you strengthen the buttons so they aren't pushed just by breathing on them, and it breaks the auto-response of conditioning to self-harm... which in turn, is a boost to your image of yourself - how you feel about yourself - and if you need a picture to see how this works: it's like taking a downward spiral... and pulling the center of it up... so that the progress goes up and forward, instead down and back into the old, scripted patterns.
She might even notice and wonder what's different about you (but don't hold your breath!) LOL...
And just like any new "skill"... you make mistakes at the beginning - it's not as easy in real life circumstances as it sounds in words - and it takes practice... which is how the old, scripted, prison-conditioning became so embedded in your brain in the first place. Practicing something new, actually replaces the old.... over time, with repetition and by learning and dissecting what goes on, when you do make a mistake or get blindsided. Don't let these mistakes stop you from trying again - the next time. It's absolutely important that you do make mistakes... so you can de-construct all the pieces of dysfunction of the relationship in your understanding and then the lightbulb will go on... and you'll catch yourself right before you get sucked in - again - and stop the whole process.
Uh, yeah - that's the goal, the golden ring, the prize. And then at that point, "mom" and her crap starts to matter a lot less as a stumbling block, obstacle, irritant, or demanding, whiny queen in YOUR life. Then, you've gained your freedom and have the opportunity to figure out what you're going to do with all that extra time and energy!!

Disclaimer: This works for me - you might need to customize it to yourself. It's a patchwork of ideas, really - a collage. The practice is still ongoing with me; I still screw up big-time... but I no longer pay such a huge price for it by taking it out on myself. That's progress, for me.
I think you're on the right track, kiddo... even though there are always times, when it doesn't feel like it and we just need someone to validate it for us. Hang in there!