She drinks coffee after coffee, saying she has only had three hours' sleep, but her eyes sparkle with joy.
Ukraine's US-born finance minister Natalie Jaresko on Thursday told AFP how she nailed the debt deal that pulled the ex-Soviet country back from the brink.
Her triumph in talks with Franklin Templeton and three other global financial titans led to a 20-percent write-down or "haircut" to the face value of the bonds they hold, a deal that saves Ukraine $11.5 billion.
This success has already led to her being nicknamed the "hero minister" by one of her colleagues in government, and a "financial cyborg" by Internet users.
"I am a little bit exhausted, but I am very happy," she said a few hours before the announcement of the agreement.
The 50-year-old sported a small gold trident pin -- the Ukrainian state symbol -- on her aubergine-coloured dress and appeared to have lost little of her vivacious energy after five months of testing talks.
"This is probably the most difficult and probably the most important thing I might ever do in my life," said Jaresko, the former director of an investment fund who grew up in the United States.
- Chicago to Kiev -
"I negotiated business transactions for two decades," she said, but "finishing any business deal does not compare to getting debt relief for the Ukrainian people."
Born to a family of Ukrainian immigrants in Chicago and brought up as a Ukrainian patriot, she came to Ukraine to head the economics section at the US embassy in the early 1990s before starting her own investment fund in Kiev.
Speaking to AFP at her ministry office, she switches from Ukrainian to English, the language in which she feels more comfortable.
Together with her children and mother, she personally took part in the Maidan pro-European protests which led in early 2014 to the ouster of Viktor Yanukovych, the Kremlin-backed president seen as massively corrupt.
In December last year, new pro-Western President Petro Poroshenko recruited her to work for the Kiev government as he handed her a Ukrainian passport.
In Kiev, she swiftly became known as "the No minister" for her rigorous stance on allocating the budget.
But despite all the problems of Ukraine's public finances, the talks with the country's international creditors proved even more complex.
She worked up to 20 hours a day, according to one of her advisors, to achieve the debt restructuring deal, even though she admitted that she had doubts it would work "every day."
"It was very hard," Jaresko said. "We needed to spend time educating our creditors that the situation was indeed critical."
Sometimes the work took a physical toll, as when she flew to California to meet the heads of Franklin Templeton personally while suffering from bronchitis.
- 'She gets what she wants' -
But for her, the real heroes in Ukraine today are the soldiers fighting against pro-Russian separatist rebels in the country's east.
"Whatever you did -- not sleep or you got sick or you did not see your kids -- that does not compare to the sacrifices they are making," she said.
Recalling the arduous negotiations on the debt, she recalled that "there was a breakthrough, basically, when we received, as the press reported, a five-percent 'haircut' proposal, which broke that psychological barrier."
"And from there, things accelerated."
The eventual agreement -- a 20-percent "haircut" off the value of the debt -- she called a "historic" achievement.
Asked how she pulled this off, Jaresko described herself as "extremely stubborn."
One of the members of her team, talking to AFP about the course of the talks several months ago, was already confident of success.
"Natalka always gets what she wants," he said at the time, using a familiar form of her name.
Jaresko prefers to downplay her role, stressing the "critical" importance of her Western allies, led by the International Monetary Fund, who put pressure on Ukraine's creditors.
"Nobody does anything alone," she said.
Some are predicting she could become prime minister, but she said she has other fish to fry, notably launching tax reform that "inspires business".
"We have no end to everyday challenges," she said, smiling.