I think I'm sort of at the opposite end of the spectrum. I never really expect anyone else to provide any kind of support, because I've never really gotten that kind of support. I'm generally the one who provides it. When people do finally withdraw, as they inevitably do, it's not really destabilizing to me because I never really relied on them for anything. I might be very sad that they're gone, but for the most part, it's business as usual.
You certainly can't change anyone, so if a relationship is unhealthy, the only thing to do is end it. I wish I could be more help.