Should a Realtor "Fire" a Client

I just fired a client. I felt uneasy at first, but I now am relieved to have these clients out of my life. You know the type, call every week complaining about the photos, where the signs are placed, why the house has not been shown more (even though the listing price was $20,000 over my market analysis). The final straw came when the client listed three items I had promised them, three items I have never promised a client, three items I do not remember ever thinking. The client said she wished she had never listed with us, so I granted her wish. I have never done this before, but these people were a nightmare.