Dear Mr./Ms. Bossname,
I must unfortunately tender my resignation, effective in two weeks’ time.
While I continue to wholeheartedly stand behind the mission and values of XYZ Organization, my experience here has not been what I was led to believe, and thus I must move on.
Specifically, I was assured that while I did not possess the entire skill set desired of someone in my position, this would be mitigated by placing me with a mentor within the company. It is only because of this promise of guidance that I accepted the role.
Unfortunately, I was thrown directly into the fire, with all of the job responsibilities and none of the support. This has been a disservice to myself, the organization, and ultimately the clients whom we so passionately serve.
I would urge your team in the future to carefully consider any promises of mentorship made to new hires. I am sorely disappointed about this lost opportunity to learn, grown, and serve my community.