Not the moment she lost her opening taekwondo fight in Athens four years ago, though that was traumatic enough; but the aftermath, the return to normality back at her parents' home in Doncaster and the realisation that her dream was over for another four years.

"I remember watching the open-top bus parade through London on the TV and seeing all the athletes who got medals," she says. "I remember Mark Lewis-Francis being interviewed about the 4x100 relay and I was just thinking, 'I wish that was me, I wish that was me'. It made me feel so sad. Hopefully, this time I'll be on the bus."

Stevenson has had enough sports psychology sessions to know that dwelling on failure does not get you anywhere in elite sport, but her Athens experience is not something that can easily be erased.

Her defeat was all the more gut-wrenching because, as a wide-eyed 17-year-old at the Sydney Olympics, she had missed out on a bronze medal by a single point.

A year later, Stevenson was the senior world champion and she went to Athens as one of Team GB's hottest prospects only to lose tamely to a woman she should have beaten. She has had four years to ponder how it all went so wrong.

"I think overall our preparation wasn't that good," she says. "We were all still too inexperienced; not just me but the staff as well, I think we over-trained too close to the competition. Now I know a lot more about the way you should train and that what I did four years ago was wrong.

"But the main thing is that I put too much pressure on myself and I just froze. I wanted to do so well, and I knew I could, but I think that affected me too much."

Four years on, Stevenson remains one of the best in the world in the heavyweight category and a big podium hope for Britain, though she is determined not to succumb to the mental pressures again. She will go to Beijing with a new mindset.

"I'm just going to go there and enjoy it and do my best," she says. "If I don't win, it doesn't matter. But if I do, it will be amazing. That's how I've got to deal with it. I'm not putting any expectations on myself."

Stevenson believes much of her success at Sydney came down to the innocence, and fearlessness, of youth.

"In those days I didn't even know what the Olympics were," she says. "When I got there I had never seen anything like it in my life.

"But in some ways it was good that I was so innocent. I didn't know anyone else in my weight category. I didn't know who was good and who was bad. I just got thrown in the deep end and I just had a go.

"I did really well, which was surprising for everybody, but I suppose I had no fear.

Now, at the ripe old age of 25, Stevenson finds herself in the role of elder stateswoman of Britain's taekwondo team. Her two other colleagues, Aaron Cooke and Michael Harvey, are 17 and 18 respectively, and are products of a well-funded support system that did not exist when she was their age.

"I think they're going to be fine because they've got such a good set-up behind them now," says Stevenson. "I never had that when I was their age. Now the preparation is so much better and they've got me to talk to about it."

Despite her new attitude of que sera sera, Stevenson would not be human if she did not hark back occasionally to the bitter memory of Athens, and beneath the laid-back exterior you sense a burning desire to make amends.

"One of the worst things was coming home and everybody saying things like, 'Never mind, at least you got there'. That's the worst thing that anybody can say and yet it's the only thing they can say.

"I'm not saying it isn't great to be at the Olympics, because most people would give anything to go there, but when you've been there twice you want to win.

"You want to get the gold or at least a medal this time. It's not about the taking part for me. It sounds ungrateful but I really want to get a medal."

Suddenly, she realises what she is saying and quickly checks herself. "But if I keep saying that, it's going to be putting too much pressure on myself," she adds.

There are clearly issues going on in the head of Sarah Stevenson, but nothing that an Olympic medal wouldn't put right.