You're feelings are a product of the way that they interact with you. I don't think you should feel bad about it. In my view/experience, it's very common for toxic parents to make their ofspring feel guilty that they they arn't doing enought for the parents. No matter what you do, it will never be enought for a toxic parent. I can totally understand what you wrote about them wearing you down. I feel the same about my parental family. From what you write I get the impression that you have a good perspective on the situation, good for you!