Why is it so easy for me to just let all of the bad stuff slide, once given a morsel of goodness?
Because your boundaries suck.
And you don't yet know how to not get reeled back in.
Part of recovery for us is to learn how to have stronger boundaries. And that goes two ways. It means, in part, to not give yourself permission to do things that aren't in your best interest. That's in addition to telling other people no.