Dear David,
I just wanted to thank you for all you have done for me over the past couple of years.  When I started seeing you I was really hurting; hating myself and trying constantly to check out on life.  I had recently separated from my wife and partner of ten years.  I was struggling to perform well at work and having a hard time finding any enjoyment in life.  I deeply appreciate all you have done to support me in transitioning to a new life.  Your guidance was instrumental in my gaining tenure, buying a new home, and falling in love with the woman of my dreams, among other important growth milestones.  I have always found you to be an incredibly sensitive, patient, and insightful person.  It’s been a joy getting to know you.  I feel deeply grateful knowing that I can call you if I ever need your support again.
Sincerely,
Tony