"I'm not naturally a combative person," he said, explaining his shock decision on Monday to quit politics midway through his second term.

"I'm not naturally confrontational.

"But every day, I have to engage in argument and debate and confrontation in one way or another, and I'm kind of tired of it."

While it may have eventually taken its toll, the NSW-born premier was hardly a shrinking violet when it came to defending the state's interests.

While in office, he publicly labelled billionaire Clive Palmer an "enemy of the state" and privately disparaged the Queenslander as "the worst Australian who's not in jail".

Those and other insults - often unprompted, at times made under the cover of parliamentary privilege - were scrutinised during a bruising defamation battle that ended with both parties being awarded damages.

At the height of the COVID-19 pandemic, Mr McGowan closed the state's borders and kept them shut for almost 700 days.

Seizing his moment, the indefatigable premier addressed the public almost every day, praising West Australians for "doing the right thing" and rebuking critics ranging from fellow state premiers to federal Liberal MPs and Qantas chief executive Alan Joyce.

With the hard border in place, WA effectively stamped out the transmission of the virus and averted the prolonged lockdowns endured by other states.

Nicknamed "State Daddy" by young voters, Mr McGowan won record approval ratings, went viral on TikTok for his musings about a NSW man fined for eating a kebab and was even immortalised in tattoos.

In millennial terms, the former Navy lawyer had already undergone a "glow-up" - shedding his glasses, sporting sharper suits and projecting a newfound confidence compared to when he entered parliament in 1996.

After nine years spent in the wilderness of opposition, including five as leader, he guided Labor to a landslide election win in 2017.

Supported by a competent and scandal-free cabinet, Mr McGowan rode his extraordinary personal popularity to a crushing Labor victory in the 2021 election which reduced the opposition to a handful of seats.

His influence was obvious as WA voters swung towards Labor at last year's federal election to propel Anthony Albanese into office.

Seemingly free of the constraints faced by most party room leaders, the factionally unaligned premier also appointed himself treasurer after the 2021 election.

He gleefully described the state economy as the "envy of the nation" after handing down a record $5.7 billion budget surplus, fuelled by iron ore.

But the premier also faced criticism over the prolonged border closures before eventually allowing quarantine-free travel to resume in early 2022.

He would later characterise the pandemic period as one of immense stress and sleepless nights.

Mr McGowan has more recently had to fend off attacks over hospital overcrowding, cozy relationships with leading business figures and issues within the troubled Banksia Hill youth detention centre.

Reports of unease within his party emerged this month after he likened riots at Banksia Hill to terrorism and claimed conditions such as fetal alcohol spectrum disorder were being used to excuse poor behaviour.

After almost three decades in parliament, Mr McGowan was quizzed repeatedly on his future plans but had insisted he would contest the 2025 election.

On Monday, after calling a snap press conference, he revealed he had been planning his exit for several months.

Reflecting on the demands of the role, Mr McGowan admitted he was burnt out and couldn't face another two years in the job.

"I just don't have the energy or drive that is required to continue in the role as premier or to fight that election," he said.

"The COVID experience, basically three years of every day standing here or wherever it might be (to address the public) ... that drained me a lot.

"Just being the premier, it drains you."

With his deputy Roger Cook among a trio of possible successors, he conceded the next premier would likely face the same challenges.

"It is all-consuming," the father of three said.

"I can't give advice on that, because I haven't been very good at balancing things.

"I hope whoever my successor is is better at it than me."

Flanked by his wife Sarah and members of his ministry, Mr McGowan said he was departing at the end of the week with no regrets and without any ulterior motive.

He had no immediate plans beyond taking a break.

Mr McGowan said he was proud to have made WA the "strongest, most successful state in the nation" while also leading a program of social reforms including passing voluntary assisted dying laws.

"It is way beyond what I could ever have imagined my career would amount to," he said.

Australian Associated Press