I know there are people in relationships who can't do that or where it might not be the best thing. For example, I don't advocate stepping away from one's child or parent (or sibling, generally), although sometimes one might have to set some boundaries. Also, sometimes it's worth going for counseling, for example, especially in marriage, whether both go for counseling together or even only one. Those relationships are not in my scope or the scope of these reflections.
I speak only from what I've experienced from my childhood. And in my experience, it feels to me that there are times to not continue to pursue a relationship, either because things have not changed enough or even simply because there is too much residual hurt.