In an interview with Forbes magazine last year, Helen Clark said the most powerful lesson she had learned was the power of persistence.
The example she gave dated to her time as leader of the opposition from 1993. Having rolled Mike Moore, her polling was rock bottom ahead of the 1996 election. She said she struggled to establish credibility. Her friends advised her to "just stand there" and her self-belief did the rest. Pressured to stand down, she stared down her detractors, including Phil Goff and Annette King. Three years on she began nine years as Prime Minister.
Helen Clark was renowned for her active role in international relations. Under her watch, the China free trade agreement was signed and it was she who kicked off the campaign for a seat on the Security Council in 2004.
She refused to send combat troops to the Iraq War in a stand that risked damaging relations with the United States after the September 11 terrorist attacks. But Helen Clark she did send troops to Afghanistan in 2001 - a decision that surprised some given her activism in anti-war protests.
That turned into a decade-long mission that resulted in the death of 10 Kiwi soldiers involved in either reconstruction in Bamiyan or training Afghan security forces for the SAS.
In 2003, Helen Clark visited Kabul and Bamiyan. She said she had no regrets about the decision to deploy.
Helen Clark's view New Zealand could not afford to be isolationist showed again more recently, when she breached her self-imposed rule not to talk about domestic politics and spoke of the need for New Zealand to be part of the Trans-Pacific Partnership despite opposition by the Labour Party she once led.
Helen Clark's influence was acknowledged long before she moved to the UN - since 2004 she has been a regular on Forbes' 100 Most Powerful Women list and she moved up into the 20s after heading the UNDP.
Her nine years as Prime Minister were not smooth. Her steel showed in her handling of the Mossad agents caught with forged New Zealand passports in 2004 - an irate Helen Clark imposed diplomatic sanctions and described it as "utterly unacceptable", "a sorry indictment of Israel".
You put in the hard yards, you do your homework.
There were bouquets that came with "legacy" policies such as reform of the health sector, Working for Families, KiwiSaver, the Super Fund, the Emissions Trading Scheme and interest-free student loans. But she was criticised for issues such as her handling of the Foreshore and Seabed Act, which saw a near revolt by Labour's Maori MPs and the walkout of Tariana Turia, exacerbated by her dismissal of protesters in a mass hikoi as "haters and wreckers".
She had to deal with the usual trials and tribulations of errant ministers. Helen Clark also got caught up in scandals of her own making - signing a painting by someone else, the speeding motorcade, Corngate.
Politics affected her personal life as opponents targeted her marriage and personal circumstances, including an allegation her husband was gay, which she said was "farcical".
Helen Clark stood down as Labour leader in her concession speech on the night of the 2008 election loss.
She refused to dwell on that loss, or in any post mortem of her time as Prime Minister, instead using her catchphrase that she had "moved on".
It was husband Peter Davis who gave an inkling of the turmoil she went through, telling Q+A she "felt rejected" and had taken some time to come to terms with it.
In 2009, Helen Clark was confirmed as the new administrator of the UN Development Programme - the third most powerful person at the UN charged with a US$5 billion budget. The global recession bit that year and one of her first jobs was to try to dissuade Governments from drastic cuts to international aid.
In the Forbes interview, Helen Clark says the lesson she learned was you had to have self-belief, which had to be grounded in "something solid".
"And that something solid is you put in the hard yards, you do your homework." That lesson on persistence may well be called on again as she tries to stare down rivals for the UN Secretary-General role.