In the high-performance world inhabited by America's Olympic swimmers, nothing is ever left to chance. Every stroke they swim, every step they take, every meal they eat is carefully planned and monitored.
But no matter how well they prepare, there are just some things no elite athlete can ever be ready for, as Missy Franklin, the rising star of American women's swimming, learned this week.
Just days away from competing at her first Olympics, the 17-year-old was living out her dream, training alongside the likes of Michael Phelps, Ryan Lochte and Natalie Coughlin at a camp in central France, when the news filtered through that a gunman had gone on a deadly shooting rampage in a crowded movie theatre in Colorado.
The man, armed with an assault rifle, a shotgun and a pistol, and wearing a full suit of tactical body armor, a helmet and a gas mask, set off two smoke bombs before opening fire in the dark theatre.
Twelve people were killed, dozens more wounded, and the news struck Franklin like a lightning bolt - for the killings took place in her home town of Aurora.
Suddenly, the golden lure of the Olympics didn't seem to matter so much as her thoughts turned to home.
"I was very, very shaken up," she told Reuters on Saturday. "It was terrifying for me because I had no idea who was there.
"I was getting information from all friends and family. The fact that so many people were hurt and so many people were affected was heartbreaking."
Franklin said she did not know any of the victims and had never been to the cinema where the shootings happened but that that had not made it any less frightening.
"I only live about 15 or 20 minutes away and I drive past it all the time because we practise there every day, so it hit real close to home," she said.
"It's unbelievable. That someone could actually do that."
Franklin's emotional state is now being monitored, and her coach Todd Schmitz, whose team is based in Aurora, said he had spoken at length with Franklin about the incident.
"I think it's made us realise that you have to enjoy every day because you never know what's going to happen. It reinforces that idea you need to stop and smell the roses," he told Reuters.
"As far as I know, none of us knows anyone who was there but I expect, in time, we will know someone who knows someone who was there, so that's going to affect your emotions."
Franklin burst on the world stage last year when she won three gold medals at the world championships in Shanghai.
At last month's U.S. trials in Nebraska, Franklin qualified in seven events for London, giving her the chance to become the first female swimmer to win seven medals at a single Olympics.
"The only thing I can do is go to the Olympics and hopefully make Colorado proud and find a little bit of light there now," she said.