I was going to share my POV, then I wasn't as it seems it's gone sideways already, but I will anyway. Maybe somebody else can relate and not feel so alone -
I have had to constantly work on this. When I was in therapy, my psychologist gave me some excellent tools. This has been invaluable.
When stuff goes wrong, I get that dialogue in my head almost instantly, like it's visceral - my so-called mother must have been right. I AM worthless. I don't deserve better, and I should not have been born.
It's taken a lot of work to stay out of that hole but I also have to keep up the work because you don't just come away from all those years of negative conditioning overnight. When I see it coming I try to just snap myself out of it and come back to the world of actual facts and reality.
I don't really care for little sayings, or cliches (especially cliches!! ugh), but I do go for pure, clinical facts. Those facts dispute all the horrible things she drilled into me and names she called me. The longer you do it, the better you get at it, but I don't know if it ever goes away completely, especially if this has been your conditioning throughout all of your formative years. These things become a part of you. But it is possible to cast them aside, in lieu of the reality in which you live now.
(not saying it's easy - it's NOT)