Dear [Recipients Name],
I hope you are doing good. I was really looking forward to this change in my roles and responsibilities for a very long time but now when the opportunity has arrived, I regret that I will have to turn it down.
As you must be knowing that I enrolled in the executive MBA course recently and I wish to complete the course because it will help me in the future in fulfilling my responsibilities in a better way. As I had taken permission from authorities before enrolling I hope this won’t affect my career path and I promise that I will take up any opportunity when it comes in the future as at that time I will not have any such commitments.
I apologize for this condition but I think we have a few more qualified people in our team whom you can select for this opportunity and they will take this up. If you need any help, let me know.