This one's a tough one.
Over the years, I've developed a mantra for relationships that have become too toxic: Love them from afar. Seems cold, right? Doesn't loving your neighbor mean holding them emotionally close to you? Giving them your time, lending them a hand, turning the other cheek? What if, at the end of that meeting, you just feel as if you've been puked on? And what if that person turns out to be the one you're supposed to be closest to, say, a parent, aunt, child, friend? What if you've exhausted all options to improve that relationship, like therapy, talking to them, letter-writing? Turning the other cheek one too many times can quickly lead to an abusive and/or masochistic situation. I mean, you deserve love, too, right? You are your neighbor.
My psychoanalyst gave me a good exercise called "active imagination" to release myself of a toxic relationship. This exercise will be different for every person, but basically, it's imagining that person in front of you, ready to listen. Then, you talk to that person from the heart as if that person were actually there, and telling them your intention of letting them go in peace. Pretty woowoo California, but it has allowed me to move on with my life. I felt at peace afterward.
One of the most helpful things anyone has ever told me is, "I don't have to like everyone." For some reason, that was a lightbulb moment for me. I don't have to like everyone! It's so liberating! I can love someone from afar, wishing them well as a fellow human being, and still keep my dignity by loving myself enough to let them go on their way.