Have you ever had to fire a client?
Yes. I tend to refer to it as, "breaking up with a client." I'm not really sure that's semantically any more positive and I've not had to break up with clients many times, but yes I have had to. Breaking up with a client is not a fun experience for either party.
Here's a thing I've learned from it.
A few days ago I posted a response to a question on 'micro-managey' clients which included a personal opinion statistic stating 9.9 times out of 10, if a client seems micro-managey, the problem is with us, not the client - thusly if WE improve our communication skills/efforts, we can significantly reduce the volume of not awesome clients. One thing I may not have mentioned is why I stand by this statement - it definitely has to do with lessons learned from good and bad experiences, including breaking up with clients.
Working with clients for more than 17 years now in the capacity of design and having my fair share of turbulent stories to tell, I learned the importance of the vetting process. We owe it to ourselves and to our clients to ask the right questions up front and determine if there is going to be open and honest communication throughout the project and personality and ethics fit before any money changes hands or any contracts are signed. It's also important to note that "open and honest communication" does not mean that things are super awesome and rosy 100% of the time. You may disagree (frequently, even) but knowing you have open and honest communication helps ensure you will hash things out in a respectful manner and arrive at a place where there's understanding.
If you're taking on every project that comes through the door just because it fits in your calendar and/or pays something, or out of sheer need for work, these are fair but it's also fair to acknowledge this will definitely set that 'not-awesome client' statistic to a much higher frequency. Putting time into evaluating the relationship up front has GREATLY reduced client break-ups for me and has GREATLY improved mutual joy in the project all around.
I hope you find some of this helpful. I'd love to hear what others have learned from the client break up process.