Thank you for this thread.
For me I had to learn that it is fine (normal?) to establish boundaries in a relationship. A relationship that is healthy is give and take.
I think knowing that sometimes I need space is healthy. I think that as a child I learned from my parents about toxic love. Their relationship was unhealthy. My dad takes hostages. After he became sober and Mom went to Al-Anon, I think she began to learn about boundaries. A person who does not respect boundaries could be termed a bully/abuser.
Setting limits is healthy. I have heard it referred to as staying inside your own hoola hoop. As adult children we have seen both parties (classic alcoholic/codependent) walk all over not only our boundaries but those of others, so some of us made the assumption that limits or boundaries are "bad" or not allowed.
Healthy people in healthy relationships know that their boundaries are acceptable. They know that they are entitled to set limits. They have this healthy behavior modeled to them instead of the very unhealthy enmeshment/hostage taking.
I know when I first began to set boundaries with my dad, he told me he was not going to speak to me again. I was finally ready to take that risk. Setting boundaries is risky because sometimes we lose a relationship. It was emotional blackmail, and when I called my dad on it, he didn't follow through with the not talking, but I was willing to try something different.
I still have such trouble setting boundaries, and I'm learning. Thank you for letting me share and for this topic. I have so much trouble with relationships of any kind.