For many giving another human being the support they require is not an easy thing. It's also about inner support and learning how to support ourselves.
Healthy support is nothing less than miraculous.
Learn the difference between boundaries and standards. Part of the challenge is to realize that those rules are definitely there and we are just not enforcing them. And yes, repeating our boundaries time and time again is part of learning how to support ourselves. John Bradshaw, recovery author and speaker, tells a story about the two lines there are to get to heaven. One line will get you straight there, the other is a how to get to heaven class.