I have been doing this, and it has led me to a place of understanding and peace. Some of the relationships that were unhealthy (to me) survived after all, and have become more healthy because of my limit setting. Others just died a natural death and I have not missed them at all.
It surprised me to know that many of the people who were abusing me stopped entirely when they knew that the relationship did not matter to me anymore. They got real responsive and made a better effort, something I did never expected.
I will confess that these are still probationary relationships.