Eliud Kipchoge has been here before, but this time is different.
On Saturday, the Kenyan distance runner will attempt to run the first ever marathon under two hours in the Austrian capital of Vienna, two years since he fell 25 seconds short.
Now he is resolute that he will break what is considered one of the ultimate milestones in athletic performance.
"I feel more prepared, I feel more ready and I am confident that I have been at that speed for the last two years," said Kipchoge, who holds the official marathon world record of 2:01:39.
"It's not something where you are thinking, 'how are we going to do it?' I have tried it a first time, and this second time I will get it."
Kipchoge's first crack of going sub-two in Monza, Italy, was part of Nike's Breaking2 project. Now he's being backed by petrochemical company Ineos in an attempt called the 1:59 Challenge.
If successful, this won't count as a world record. In fact, Ineos hasn't even submitted a request to the IAAF for the attempt to be officially ratified.
Kipchoge will follow behind a car -- a condition not allowed under IAAF sanctions -- and is being assisted by an army of 30 pacemakers.
He will run a six-mile, tree-lined stretch 4.4 times in Vienna's Prater-Hauptallee (main avenue), chosen because of its flat gradient and the city's mild climate.
Kipchoge, the reigning Olympic marathon champion, is aware that there are critics of the manufactured conditions surrounding the attempt.
"The law of nature cannot allow all human beings to think together," he said. "In breaking the two-hour barrier, I want to open minds to think that no human is limited. All our minds, all our thoughts are parallel. But I respect everybody's thoughts."
He added that the 1:59 Challenge is different to competing in a race like the Berlin Marathon, where he set the current world record in 2018.
"Berlin is running and breaking a world record," said Kipchoge. "Vienna is running and making history -- like the first man to go to the moon."
The comparison to Neil Armstrong's moon landing -- one that Kipchoge has referenced a number of times in the buildup to Saturday's race -- has been probed: "Getting man to the moon involved overcoming gravity," leading sports scientist Ross Tucker told CNN in August. "What Kipchoge is doing is taking gravity out of the equation."
It's a time when it's easy to be cynical about athletics.
Leading coach Alberto Salazar has been handed a four-year suspension for doping violations, sprinter Christian Coleman has been criticized for missing drugs tests, and the recent world championships were played out in front rows of empty seats in Qatar.
But Kipchoge admits that his intentions are pure and simple. He wants to push boundaries and he wants to make people smile.
"I am running to make history," he said. "I am running to tell people no human is limited. It's not about money. It's about running and making history and changing people's lives.
"I am calm and I'm really looking forward to Saturday."