Needless to say, he didn't need to find another job.
"I just managed my own money," says Couillault, who also spent the time with his young family, took big overseas trips and got involved in his children's school and community life.
He began investing in property - both direct and listed property - and in small businesses.
"I took a small interest in a baby food company, we took an interest in a restaurant pub and helped Generate KiwiSaver launch."
Not all his investments panned out.
Couillault bought a cornerstone shareholding in pre-mixed drinks company VnC Cocktails in 2010, but by 2014 it went into liquidation after attempts to sell the business failed.
"That was a start-up that didn't survive," he says. "When you look at these things it is always a portfolio approach."
He says that experience was a good reminder about the need to diversify investments - not putting too many eggs in one basket.
In 2011 he paired up with rich-listers the Spencer family to launch Richmond Investment Management, a managed fund partnership.
Couillault remains a director and chief executive of the firm, which requires a minimum investment of $25,000 into its funds.
His public persona stepped up a notch last year when he and wife Sarah sold their family home in Remuera for $18 million - one of the biggest house sales of the year.
Couillault is nonchalant about the deal. "It was an out of the blue opportunity," he says.
The house is said to have been sold to a wealthy American, and Couillault says the giant pricetag didn't faze him.
"In terms of the transaction itself, we deal in investment markets with big figures all the time.
"Fortunately, we were able to buy a big family home in the same neighbourhood."
Growing up in Papatoetoe - or Papa Two Toes as he calls it - the idea of selling a house for that kind of money was "definitely not" something he ever dreamed of doing.
Never a big achiever at school, Couillault says it was when he hit university and began studying economics that something clicked.
He started his career at Westpac as a stock market analyst.
A six-year stint with UBS saw him move to Sydney and London before returning to New Zealand, where he lined up the job at Fisher Funds.
Couillault's other big move last year was his decision to buy an 80 per cent stake in Macquarie Private Wealth - a financial adviser network owned by Australia's Macquarie Bank.
"I got approached about it a year ago from people within the Macquarie Group who said they were looking to sell and introduce local ownership."
Since buying into the business, Couillault has reduced his stake to 45 per cent, with the management buying about 35 per cent.
The business was re-branded at the end of last year, changing its name to Hobson Wealth Partners.
It's a major shift for Couillault, who has previously managed money on behalf of others but has not been involved in offering personalised financial advice to the public.
"It is where the rubber hits the road," he says.
Couillault sees it as a great opportunity to establish and grow a business which already has a nationwide presence.
While 35 of its 50 advisers are Auckland based, Hobson also has people in Wellington, Christchurch and Queenstown.
On choosing the name, he says, "we wanted a name that was nationwide, strong and had heritage."
Hobson is a nod to William Hobson, New Zealand's first Governor.
Hobson's client base is a mix of small institutional clients and wealthy retail clients, to whom it offers tailored financial advice.
Couillault says there is a growing demand for advice, driven by a generation of baby boomers who are selling their businesses and looking towards retirement, as well as the new migrant population which has exploded in recent years.
He is looking to increase the number of clients this year and is also considering adviser growth, through buying or joining up with complementary businesses.
"Size and scale is of paramount importance in this industry," he says.
"The way to fund a cost base that provides the services we want is to be bigger."
The advisory industry has been consolidating in the wake of licensing and an overhaul of compliance following the global financial crisis and fallout from the David Ross collapse, in which clients lost $6 million.
Couillault says concerns about trust are nothing new. "I can remember that underlying issue going back for the last 20 years."
But he believes there is now more understanding about the need for proper financial advice, and he puts that down to KiwiSaver.
"I think in spite of the odd occasion of rogues ... there is a slowly building understanding of the requirement for proper advice."
He says KiwiSaver is the top priority for New Zealand's financial services sector, although he admits the average balance, at $13,000, is still too low to attract proper personalised advice.
"It's getting there. But it is probably not yet there."
When it gets to be the second largest asset after the family house, then advice will play a bigger role.
Couillault believes it will be another five years before that happens.
In the meantime, he recommends that people do as much homework as they can to find out about their KiwiSaver fund.
One solution coming to the fore is robo-advice, which a law change this year is expected to make possible in this country.
Couillault admits robo-advice - where people punch their details into an app and get told what to do, based on mathematical algorithms - is the biggest challenge the advice industry currently faces, but says his firm is prepared to embrace it.
"We will do some analysis on the best way to tackle this. Do we want to get involved in that space, and if we do, how do we do that?"
He expects artificial intelligence will become more and more prevalent, particularly in KiwiSaver, because there are many people with very small balances.
But for now, he says his focus is on getting his advice business to be the best it can be.
Warren Couillault
Job: Executive director, Hobson Wealth Partners
Age: 48
Family: Married to Sarah with two daughters and a son
Last film seen: Star Wars: The Force Awakens
Last book read: Homeward Bound, The Life of Paul Simon
Last holiday: Long weekend at Omaha Beach with family and friends
