Hi [Boss|your manager name],
I feel sorry to say that I decided to pursue an external opportunity. Maybe it is really a surprise for you. After serious and careful consideration, however, I have to make this adjustment regarding my personal career development plan. I’m sorry about the inconvenience it may bring to you and our team.
The decision is really hard for me because I have so enjoyed my working relationship here. Our team has offered me great latitude and opportunity within our business area. And as a result, I’ve not only gained the technical skills, interpersonal skills, but also learnt a lot on predominant company culture and the art of management. I’d like to express my deep thanks for the rewarding experience I’ve enjoyed during those days.
However, all good things must come to an end. I have to say goodbye to you and our excellent team. I will be dedicated to hand over all my work to the appointed personnel before my departure. I would like to take this opportunity to thank again for your kindly support and instruction during my work.
Wish you every success in future!
Regards,
[your name]