"You get to the stage where everything is 'been there done that'," he said. "I really don't want to get stuck doing the same thing."
QE had been in "a pretty bad way" when he arrived but he was confident it was now a thriving and viable business, albeit with some challenges.
A "damn good team" was there and he would keep an interested eye on how they got on.
Mr Sharplin said he and his English wife had considered moving their family back to the UK but decided against it.
"There's a few other things I'd like to get my teeth into. Rotorua has got a lot of opportunities."
While he wouldn't reveal his plans, he said he would be broadening his interests beyond the healthcare sector.
Mr Sharplin described his time at QE as challenging but said he had loved it. And he was looking forward to using his farewell gift - a six-month QE gym membership.
He admits to one regret - "when I started, I said if I don't do anything else I am going to get it [hospital] painted".
It was only about 70 per cent painted, he said.
QE Hospital Ltd director Paul Sampson said when Mr Sharplin was appointed they were looking for someone who could turn the organisation around.
"He was the sort of guy who wanted to get out and do things. That was his motivation, he liked being a mover and shaker," he said.
"It was always anticipated the type of person we wanted to change may not be the same person to carry on ... not in a negative sense."
About six months ago, he and Mr Sharplin had discussed QE entering a consolidation phase after a period of "change, change, change".
"That was Peter's expertise and we were pleased to get him on board. We're pleased with what he's done."
Former QE financial officer Kate Gillam has been appointed acting general manager and will be assisted by former Lakes District Health Board chief executive Cathy Cooney.
Ms Cooney, now a consultant with Kowhai Health Associates, will conduct a review of the organisation.
Mr Sampson said: "Over the next few months we're doing a total restock of where we are at, what the future is.
"It's an opportunity to run the ruler over the company using someone who's got expertise."
When the report was completed the company would look at appointing a new general manager.
"We're confident that there is a sustainable business there. It's to the point, it's as lean and mean as it can be. It's [now about] how we expand into the future."
QE could no longer rely on being funded by the district health boards but must push harder into the private market.
"[It] needs to be taken from public health system to private company," he said.
