Dear John:
This letter is to inform you that I am concluding my employment with (company) effective as of (date).
The time I have spent at (company) has been most rewarding and helpful in my career, and I hope that my contributions to the company have been constructive.
My relationship with you has always been professional,
warm, and results-oriented.
If I can be of any special assistance during my final two weeks, please feel welcome to call on me.
Sincerely,
Your Name
"Human beings, by changing the inner attitudes of their minds, can change the outer aspects of their lives."
--William James