Hi Overcomer,
I think the guilt is very normal and I have struggled with it for years. I remember being in counselling sessions years ago and telling the therapist that standing up to my mum felt like kicking a puppy. She has always been very good at manipulating people into feeling sorry for her and portraying herself as a victim. I think when you are used to putting someone else's needs first it does feel 'wrong' to stop doing that, especially as, is often the way with parents, that it might come about when they are frail and elderly.
I think perhaps the thing to do is just try to accept that you might feel guilty but not let it guide you, if that makes any sense. I have spent years having to keep telling myself that I'm not doing anything wrong, I'm just refusing to allow my mum to treat myself and my son badly. No-one should feel guilty about refusing to be abused, but I think part of the abuse mentality is that we convince ourselves or are convinced that it's our fault. I think I was also taught for years that I was responsible for how my mum felt and she used to make me feel terribly ashamed of hurting her feelings when I was younger. Obviously as a child you don't have the objectivity that you have as an adult. My mum, for example, would act incredibly wounded over something simple, like myself or my sister not offering her a cup of tea when she got in from work or getting the hoovering done while she was at work. She sometimes go days without talking to us over something like that. I used to feel like I was dying inside and would tie myself in knots trying to get her to talk again. Eventually she would and the relief was so huge, it meant all the stuff that went before didn't matter.
So I do think there can be old patterns that are incredibly hard to break but for me once I become aware of that it seems to help, for some reason? So perhaps now you notice it it will start to lessen? But for me I have to tell myself that I am doing the right thing and not let myself beat myself up over it, if that makes sense.
Keep on keeping on!