Troon - American star Jordan Spieth admitted that his last-minute call to pull out of the Olympics was the "most difficult decision" he has ever had to make.
The 22-year-old Texan became the latest big name in men's golf to withdraw on Monday, when the list of players to go to Rio de Janeiro next month was announced.
Number three-ranked Spieth joined the other members of the world's top four, Jason Day, Dustin Johnson and Rory McIlroy, in pulling out amid widespread concerns over the Zika virus.
"Listen, this was probably the hardest decision I've ever had to make in my life at 22-years-old. I can probably honestly say that," Spieth said at Troon in Scotland, where this week's British Open will be held.
"This was harder than trying to decide what university to go to. Whether to turn professional and leave school. This was something I very much struggled with.
"I bounced back and forth, and ultimately a decision had to be made yesterday, and so I made it," he said.
"It will loom over me throughout the Olympic Games, for sure. I will be, I'm sure at times pretty upset that I'm not down there. I thought about all this ahead of time."
Spieth denied that his withdrawal was specifically for fears of catching the mosquito-borne Zika disease and accepted that it could be an over-reaction on his part and that of his fellow stars.
He also refused to confirm what medical advice he had been given to help him reach such a decision.
"No, that's personal. I can't. I can tell you that I'm not specifically pinpointing any one thing in my health concerns either," he said. "This is health concerns as a whole."
The withdrawal of Spieth, who won the Masters and US Open last year, means that six of the world's top 10 will not be at the Olympics, with Australia's Adam Scott and South Africa's Branden Grace also opting to miss out.
That has damaged golf's reputation as an Olympic sport as it returns to the Games for the first time in 112 years.
But Spieth insisted that he wants to take part in the next Games in Tokyo in 2020.
"I'm very passionate and very much a supporter of the Olympics and Olympic golf. I do hope to play in four or five, you name it, Olympics representing the United States in the future, if I have the opportunity," he said.
"Unfortunately, this is going to be a very, very difficult thing for me to do to watch the opening ceremonies and watch my peers compete for a gold medal or any medal, and watch people stand on the stage and hear the national anthem playing.
"I certainly have thought about all that and it's something I've looked forward to since 2009 when it was announced. But I'll make it a goal to be at Tokyo in 2020. I'll make it a significant goal."