_________________ has always been a strong supporter of individual growth, and it has always encouraged its employees to make the most of their personal capabilities. It is thus with deeply mixed emotions that I write to tell you that an opportunity has presented itself to me which I feel I cannot in conscience refuse. In order to avail myself of this opportunity, I must leave _________________, effective _________________.
_________________ has been a nourishing and productive environment for me, one in which I feel I have come of age as a professional. I was not pursuing other opportunities, but when I was approached about the possibility of becoming _________________ at _________________, I felt I owed it to myself to learn more.
In the end, the combination of professional challenge and financial incentives made it seem that the time had come for me to move on.
Please know that each of you will always hold a special place in my mind. I will be glad to help train my successor, and will continue to be a strong supporter of the work of _________________.