I highly recommend this book: https://www.amazon.com/Adult-Children-Emotionally-Immature-Parents-ebook/dp/B00TZE87S4
It helped me understand that I didn't need to feel guilty. Setting boundaries is the only way to get out from under it. You can do it. Doesn't mean it won't be painful, but it gets easier. It really does. And you'll be a better person for it.