What do healthy boundaries look like?

Hi! This is my first question- just joined yesterday-Yay!

I just had an amazing coaching call with Madeline. I thought I would be coached on my sister in law, but it turned into being coached on my own thoughts and how I beat myself up because I “should” be managing my mind around an abusive person, and beating myself up for even needing to set boundaries.

My question is about healthy boundaries and what those look like. I have always had the thought that if someone is family, you should just do whatever is humanly possible to maintain that relationship. I see now that not setting boundaries is really me not taking care of myself. I would really like to change that. I usually practice a black and white version of boundaries which is either “ALL IN” or “avoid all contact”, but is there something better? I don’t have a lot of experience setting boundaries in a healthy kind of more gray way. Can you help me with that?
Thank you!