To Whom It May Concern (or add your managers name here):
I regret to inform you that I am resigning from my position as XXXX effective, October 11th, 2018 (two weeks). I have been presented with an opportunity for a chance to take on more responsibility in a unique role at another firm.
I have enjoyed my time at XXX along with all of the colleagues I have come to know and respect. In my X years of service, I have learned so much and am very appreciative of all that you have shown me and value your leadership and expertise.
The decision for me to accept this new job did not come easily but I feel that it is the right choice for me at this time. Thank you for all the support you’ve provided over the years and I hope that we can keep in touch.
Today I Quit My Job