The council head announced her resignation from the role on Wednesday, and will leave the job on December 14.
She plans to stay in Central Otago, but has no immediate career plans.
"I had been talking about it with my husband, Colin, for a few months. The boys leave the nest soon, so now is time to have more flexibility in what I do and have more time for them."
She loved the effect the council had on the community, she said.
"When I came in I wanted to revisit how we were of service to our community. How we greet people and how we engage with people is important to me."
She was confident in the council’s ability to manage the growth of towns like Cromwell and Alexandra.
"Cromwell is kind of a law unto itself, because the growth there is exponential. It will be important for council to keep planning ahead and to share the cost of infrastructure, especially things like water, with future generations."
The council was "caught out" at one stage because it did not have the resource consent staff to handle the level of inquiries.
Ms Mash said she was proud of work, still in its early stages, the council was doing in Clyde to manage the growth of tourists to its centre and bring a sewerage system to the town.
She came into the job in February 2015 as the council’s first female chief executive.
Being a woman did affect the way some people interacted with her, but "not for better or worse", she said.
"There’s the notion that I will have a softer skill set, and I do, but I’m no pushover.
"A big part of the job is to say no in a way that people will accept and respect."
Central Otago Mayor Tim Cadogan said Ms Mash would be "terribly missed".
"Our philosophy is that no-one is irreplaceable, but she is very easy to work with and worked hard on service-focused change."
Helping to replace her would be one of the "biggest decisions" in his tenure, he said.
