Dear__________，
IamsureitwillcomeasnosurprisethatIwishtoresignmypositionas__________.ThoughIhaveenjoyedworkingwithyouandothercolleaguesinthecompany/organization，thereareafewreasonsthatforcemetogiveupmycurrentwork.
Foronething，__________.Foranother，__________.Moreover/Besides/Inaddition，__________.
Iappreciatetheplentyofhelpandencouragementfromyouconstantly，andIamverysorryforanyinconveniencethuscaused.IpromisethatIwillstaythroughthenextmonthtohelpyoufindareplacementformyposition.
Sincerelyyours，
LiMing