This is a tough conversation. Ensure you carefully note the customer journey and present it to your boss. Explain why you think it’s time to move on and how you can use the free time to better serve other customers.
Every situation is different and will require different customer engagement strategies. Weigh the costs of making a customer happy against those of letting them go.
The customer isn’t always right, but often they are. You must decide how to prioritize your needs against those of your customers. However, never turn your bad day into a bad customer experience.