The sentence "I left my post" is correct and usable in written English.
You can use this sentence when referring to the position or duty you used to have or took part in. For example: Yesterday, I left my post at the reception desk to go to my doctor's appointment.
I had not heard from Reiko-san since 2003, when I left my post as the Guardian's Tokyo correspondent.
I left my post as director of LID in 1960 and became an editor of a short-lived monthly public affairs journal that deserved its early demise.
"That's why I started the Teaching Fellows program in the New York City public schools, and that's why I left my post to come here and lead the campaign for public education".
When I left my post at the beginning of 2001, the population was approaching 500 wolves, and for the next ten years recovery continued apace.
I leave my post as chief executive of the NHS Confederation this week to return to being chief executive of an NHS foundation trust.
As I leave my post as world affairs correspondent for the BBC News website, I would like to reflect on the shock I experienced nine years ago when I left the "mainstream" BBC to join the then orphan child of News Online.
The thing I'll miss most when I leave my post as VP of Marketing at Virgin America — other than skipping the TSA line and our amazing teammates — is seat 4C.
In March, I officially left my post at NCI.
"If I say I'm leaving my post, I believe that's irresponsible and will bring more uncertainties," he said.
The 37 year-old said on Zenit's website: "At the end of the last season the club offered me the chance to extend my contract, but I refused this offer and at the end of this season I will leave my post.
More specifically, I left my first post-M.B.A. job in finance (in equity at a French bank) after only two weeks.
