Carwyn Jones thinks the lesson is that the party must show it is distinctly Welsh.
Voters aren't interested if they suspect someone in London is pulling the strings, he says.
"We suffered in 1999 because we were seen as a party being controlled by London and we have to accept that. That's not the case any more."
Between now and polling day on May 5 he'll be doing his best to convince you that Labour has learned that lesson over the last 17 years.
Labour wants its campaign to have a distinctly Welsh flavour. That's why its Welsh leader will be front and centre throughout.
He wants another five years in power to complete a "decade of delivery" that started in 2011.
But opponents say he's had long enough to deliver. He's been first minister since 2009. Labour has led the Welsh government since 1999.
On a campaigning visit to a day care nursery in Cardiff, he brushes aside that criticism.
"I think we've delivered a huge amount for people," he says.
He cites "ground breaking laws" on organ donation and Aston Martin's recently announced plans to build luxury cars in south Wales.
Were it not for devolution, "we would have a junior doctors' strike".
But the opposition parties see it differently. Were it not for Welsh Labour's devolved government, we'd have shorter waiting times in the NHS, according to the Conservatives.
Labour's record in the health service will be the big battle ground in the election - an election Mr Jones says is "a straight fight" with the Tories.
He says UKIP pose a threat to Labour too, but in our interview - as in his Welsh Labour conference speech last month - he doesn't mention Plaid Cymru at all.
It's a reflection of Labour's strategy to convince voters this is an either/or election: either keep Carwyn Jones as first minister, or hand over the reins to Andrew RT Davies, the Welsh Conservative leader.
But could that strategy be undone by the spectacle of Labour MPs feuding with each other in Westminster since Jeremy Corbyn was elected leader after last year's general election defeat?
"What we've seen in London hasn't helped. Nobody could pretend otherwise," he says.
"It's calmer there now but people don't like parties which are fighting with each other."
He adds: "What we've said to people is as Welsh Labour we're united. We've got a programme going into the election. I'm the leader.
"And the policies that we will develop in Wales, the policies we will put in our manifesto, are all crafted in Wales.
There's no influence over those policies in terms of our colleagues in London. They wouldn't seek to influence our policies anyway."
Mr Jones likes to call his Welsh government a "pro-business government".
I ask him whether that's his coded way of distancing his administration in Cardiff from the left-wing politics of Mr Corbyn and his supporters.
"No. This is my way of differentiating Welsh Labour as a party. I would do this regardless of what the situation was in London," he says.
"We've done it in elections past. People in Wales want to support parties that they feel have a degree of autonomy, enough of a degree of autonomy, that makes them a properly Welsh party with roots in Wales."
He denies that his "decade of delivery" is a hint that, if he wins, he's planning to stand down at 2021 election.
He and wife Lisa have a son Ruairi and daughter Seren, both of whom are at school. Does he ever wonder about life away politics - a life where he could spend more time with them?
"The honest answer is yes, it has been difficult for the family. My children have only know me as a minister and you do make sacrifices in this job.
"When I get spare time I do spend time with the family. It means you've not got much time for anything else."
But he adds: "I love the job. It's for other people to decide whether I stay in it obviously. You couldn't do this job if you didn't like it."
Those other people - the voters - will make their decision on May 5.

Sum: What has devolution taught the Labour Party?


The figures, requested by the Scottish Tories, showed that £33.2m was spent settling 13,000 claims from 2007-2012.
The party said it suggested there was a "compensation culture" which was "spiralling out of control".
The council umbrella body Cosla accused the party of "opportunistic council bashing".
Its president, Councillor David O'Neill, said local authorities only paid compensation when instructed to do so by their lawyers.
The Conservatives' local government spokeswoman, Margaret Mitchell, said it was "neither sensible nor sustainable" for local authorities to be spending millions on compensation payments when public finances were being squeezed.
She said the payments were made over incidents ranging from the "very serious to the utterly ridiculous".
Settlements included a man in Edinburgh who claimed £170,000 because a firework blew up in his hand and a woman in Clackmannanshire who claimed £40 because grass-cutters damaged her garden gnomes.
A dog owner in East Dunbartonshire received £57 from the council after their pet's paws were covered in tar and a cyclist in Edinburgh was given £4,000 after being knocked off their bike by overhanging branches.
Of the local authorities which responded, Falkirk Council has paid out most, at about £6.7m, while claims cost Fife Council more than £5.2m over the period.
Edinburgh City Council spent just over £3.2m but at Glasgow City Council - Scotland's largest local authority - the cost was £665,000.
Across Scotland, the majority of claims involved vehicle accidents, trips on pavements or potholes and problems with council housing.
Ms Mitchell said: "It is right when someone is injured, has their property damaged or is inconvenienced through no fault of their own, councils should pay up quickly and efficiently.
"However, the sheer amount of cash involved here really points to the compensation culture in which we live spiralling out of control.
"Councils must be given the appropriate legal support when people make spurious claims. Clearly, with budgets tight, it is neither sensible nor sustainable to be spending millions of pounds every year on incidents which, in many cases, are entirely avoidable."
The Conservatives claimed the true figure could be even higher as seven of Scotland's 32 councils did not respond to the request.
But Cllr O'Neill said: "The Conservative Party have certainly chosen to have Scotland's councils in their sights over the festive period. Here we have more opportunistic council bashing from them.
"They should perhaps remember that councils are made up of all political parties and as they returned an increased number of councillors in the May elections, they are having a pop at themselves to a large extent.
"The bottom line is that in the modern world we now occupy, there is far more of a compensation culture and people are often actively encouraged to pursue claims through no-win no-fee lawyers.
"However, that said, councils only pay compensation when they have been instructed to legally. They do not pay it willy-nilly and to suggest otherwise is both wrong and misleading."

Sum: Scottish councils paid out more than £33m for compensation claims over the last five years, figures released after a Freedom of Information request show.


Rose, 26, has not played since damaging medial ligaments at Sunderland on 31 January but had been expected to return before the end of the season.
He recently returned to training but it was discovered "the problem has not resolved fully", a club statement read.
"Therefore a decision has been made to proceed to surgery."
Rose made 21 appearances for Spurs this season, 18 of those in the league, and scored two goals.

Sum:
Tottenham and England left-back Danny Rose has undergone exploratory surgery on his left knee, delaying his return from injury until next season.