How do I end a client relationship professionally?

You have learned to end client relationships professionally, closing them when they no longer serve either side while protecting your name. That is a mature skill, and it is worth naming plainly, because knowing how to end things well is as valuable as knowing how to begin them. The heart of it is respect: for the client, for the work you shared, and for yourself. A professional ending is honest about the why, gracious about the past, and clear about the handoff. It leaves the other person with their dignity intact and leaves you with a reputation people trust. Endings done well often bring referrals, not resentment. Keep doing what you do, and add one small thing: after each ending, leave the door open with a genuine line, a referral, a good word, or a simple it was good to work together. The way you close a relationship is remembered longer than most of the work in the middle. You clearly already know that. Keep it up.