Usain Bolt says he has overcome injury problems and is ready to defend his Olympic titles as London 2012 gets ready for the opening ceremony.
Friday night's three-hour spectacle in the Olympic Stadium is expected to be viewed by a billion people worldwide.
More than 10,000 athletes from 204 nations will take part in the Games.
And Bolt, who promises to be one of the star attractions in the 100m & 200m, said: "This is the moment that is going to define my entire life."
Usain Bolt wins three gold medals at the Beijing 2008 Olympics
He added: "A lot of people say I am a legend, but this is going to define me as a legend."
The reigning 100m and 200m champion was
beaten in both events at the Jamaican trials
by training partner Yohan Blake and has been struggling with back and hamstring problems in the build up to the Games.
"I think I am probably 95% fit but I am in great shape," Bolt told BBC sports editor David Bond.
Bolt, who will be Jamaica's flag bearer at the opening ceremony, also hinted he may go for four golds by running in the 4x400m relay, as well as the 4x100m.
"If I feel like I'm up to it after the 200m, then why not? For my country, I would do it, if it was necessary," he said.
Bolt's fitness has been a source of speculation following his defeats by Blake. But the 25-year-old says he is fully focused on the Olympics.
"It is perhaps no surprise that I found a slightly more humble Bolt when I interviewed him, just a day before he was due to carry the Jamaican flag at the opening ceremony."
"It's always a wake-up call to get beaten. It opened my eyes and I sat down to rethink a few things," he said.
Bolt was speaking four years to the day since he smashed the 100m world record at the 2008 Beijing Games with a time of 9.69 seconds, despite slowing to celebrate yards from the finish line.
He broke his own record a year later with a time of 9.58 secs at the World Championships in Berlin, before losing the world title to Blake in 2011 when he was disqualified after a false start.
Bolt also spoke to the media at an event in east London, which featured countryman and fellow sprinter Asafa Powell.
He said: "The vibe is good and I am happy. I am always ready. For me, I keep telling you guys it's always about the championships, it's never about one run, never about the trials."
See how the men's 100m and 200m sprint world records have progressed over time with BBC Sport's Olympic graphics.
The smile was back on the face of the sprinter, as he entertained the world's media, but he admitted it has not always been easy to keep it there.
"I've been through so much, with niggles and problems, and I have to do a lot of sponsorship stuff as well," he said.
"There are so many different things that I have to do and I have got to keep focused on going out there and competing and training every day.
"It's getting harder and harder just to smile because there is so much on my mind, worrying if everything is going to come together and a few other things.
"But I think I am more confident now that everything is feeling better, so I can smile more now and I am looking forward to it."