Dear Mr./Ms. Bossname,
I have agonized over this for weeks, if not months. I must tender my resignation, effective in two weeks’ time.
I will cherish my time at the company, from the people I met to the skills I learned. I am grateful to you, specifically, for your guidance and mentorship. It is due to your kindness and expertise that I am able to make this move in the best interest of my career and my family.
This is truly one of the most difficult decisions I have ever had to make. Thank you for your support.