Roger Federer admitted he could not comprehend his achievement after winning his third Grand Slam of 2004 at the US Open on Sunday.
The Australian Open and Wimbledon champion thrashed Lleyton Hewitt 6-0 7-6 (7-3) 6-0 for his first US title.
"Not in my wildest dreams did I think I would win the US Open, it's still tough to believe," said Federer.
"At the end of the year I'll probably look back and think 'how in the world did I do that?'"
Federer, who also won Wimbledon in 2003, now has four Grand Slam titles and, at the age of 23, is increasingly compared to 14-times Grand Slam winner Pete Sampras.
"There are still plenty of other guys in front of me, not just Sampras," said Federer. "It's not a goal for me to beat Pete's record. For me that is not the motivation.
"Last year was a great year, winning my first Grand Slam title, but suddenly I'm sitting here this year
with nine (tour) titles. It's insane.
"But I'm still at the beginning. The road is long, there's a lot of hard work to do and you never know when the day might arrive that you are sick of travelling.
"Right now I'm enjoying life as world number one and I want to stay a bit longer."
Hewitt admitted he had no answer to Federer's blistering form in the first and third sets of the final.
Asked if he felt anyone could live with the Swiss in that form, he said: "I don't think anyone in this tournament ... maybe Pete Sampras.
"After Pete left, Roger has come in and that could help tennis in the big picture. He is still only 23 years old and I think he is definitely going to be one of the greats."
Hewitt was able to exert some pressure in the second set but could not stay away from the top seed's lethal forehand.
"When he is on fire with his forehand like that, it's hard to get it to his backhand," the Australian said.
Afte coming into the final on the back of 16 straight wins and two titles, Hewitt had reason to remain positive.
"It has been a great four out of five weeks for me," he said. "It is obviously disappointing, my first loss in a Grand Slam final.
"But when I look back it has been great tennis for me the whole time. When you put yourself in a position to play for Grand Slam finals, that is what I play tennis for."