How do you handle a situation where a promising employee’s performance suddenly drops and they're in denial about the problem?

For therapists who work relationally with attachment due to trauma. Have you ever had clients who you were attached to and the were they were attached to you? At the end would you tell them the love stops with therapy as in no more I love yous?
What are some ways to ensure a smooth handover of your work if you suspect you might be laid off soon?