It IS a dilemma unique to the pinnacle of professional sport.
Sitting around the Christmas dinner table, relaxed and perhaps enjoying a well-earned glass of bubbly with family and friends, you are struck by the nagging thought that right now, somewhere in the world, your rival is hard at work, training to beat you.
It was always the boast of the great decathlete Daley Thompson in the Eighties that he trained three times on Christmas Day, because he knew his great foe, West German Jürgen Hingsen, did not do as much.
As she prepares to enter the biggest year of her life, Jessica Ennis has no such concerns. As the nation picks up the Olympic baton, Ennis, already the poster girl for Team GB, is also one of the great gold medal hopes.
But as she drops in on her old school – King Ecgbert in Dore, Sheffield – Ennis is a study in composure and confidence, with plenty of steel mixed in.
“I won’t be training on Christmas Day,” she says. “But I’ll be back at work on Boxing Day.”
Her trans-continental heptathlon duel with Russian Tatyana Chernova may have some way to run to match that of Thompson and Hingsen, but we can expect some hefty blows to be landed in 2012.
Ennis took the honours in 2010, at both the World Indoor Championships in Doha and the European Championships in Barcelona, but, tellingly, Chernova struck back at the World Championships in Daegu in the summer. They will next slug it out at the Hypo Meeting in Gotzis, Austria in May and then, of course, in London.
It is a visual representation of this disappointment that is driving Ennis on to greater heights next year.
You probably saw it in the newspapers – the final moments of the 800m in Korea, Chernova pointing skywards in victory as she crossed the line, Ennis’s face a picture of dejection as she realised she would have to settle for second-best in a multi-events competition for the first time since 2009.
“She is really celebrating while you can see in my face that I’m gutted,” says Ennis. “That image stays in my mind because I don’t want to be in that position again.
“I’m definitely going to get a print of it, but it’s already ingrained in my mind. When you think about situations like that, it can help you to push yourself a little bit more.
“I had the drive before, but it’s made me work harder. I’ve got that image in my head of the whole Daegu thing and that does push me on. I’ll have it somewhere so I can have a sneaky little look every now and then and add a bit of fuel to the fire.”
Ennis is diplomatic in talking about her relationship with Chernova, who has overtaken Ukraine’s Nataliya Dobrynska and Germany’s Jennifer Oeser as her greatest challenger. In searching for the right adjective, she rejects the journalists’ suggestions of “moody” and “severe” in favour of “strong, stern and straight-faced” and offers a tiny insight into the psychology of competition.
“We’re just very, very different. I didn’t know that was kind of a Russian thing, she comes across quite straight-faced.
“I obviously just see her when I compete with her and she speaks a bit of English, but not really good English.
“There’s definitely a sense of camaraderie after the event but we are all competing at the end of the day.
“But I don’t really want to have a nice, fluffy conversation with her during a meet.”
Locked in an ongoing rivalry, the pair keep inspiring one another to even higher standards. Ennis is under no illusions that it will most likely take a British record score to claim Olympic gold – her best is 6,823 points, eight short of Denise Lewis’s national record, but Chernova won the World Championships with a total of 6,880.
“I definitely think it’ll take a British record after what Chernova achieved this year, it’s going to take 6,900 to win,” says Ennis, not the slightest bit fazed by the spiralling numbers.
While the nature of the event requires fraction-by-fraction improvement across all disciplines, she will focus on some specific areas.
The javelin is top of the checklist. An underwhelming best of 39.95m cost Ennis her world crown in Daegu, but she is adamant this will not happen again.
“I’m not going to let it become an issue. We have two sessions a week with javelin as we’ve always done and we’re working on our run-up to get that really engrained.
“I’m just making sure I’m really comfortable and really confident with this event. I don’t want to dwell on it and make it into a big issue and start flapping and panicking about it because I don’t think that’s the case. I’ve had some really good sessions already this winter and I need to keep working on it and drilling it. I hope to find a few points in most of the events.”
Similarly with the long jump, where Ennis hopes some minor technical adjustments will deliver the extra 10 or 20 centimetres that could prove the difference between success and failure.
As if all this was not enough in an Olympic year, Ennis also has a busy indoor season to work towards, including the AVIVA Indoor UK Trials and Championships in her home city of Sheffield and the AVIVA Grand Prix in Birmingham in February, and the Indoor World Championships in Istanbul in March.
“We’re having a discussion over which events we can fit in there. I just want to cover all of the events before the World Indoors.
“It would be a nice start to the outdoor season to go to Gotzis and compete against all the top heptathletes at the Olympics and it would be an ideal start but I’m not going to get fixated on ‘I need to do this to be successful at the Olympics’.
“I’ll take my own path there and I just want to get into the best shape possible and remain healthy and injury free. And just be competitive at all competitions.”
Ennis’s dazzling smile was much in evidence at her old school – report card: good at English and PE, talks a lot – as teachers passed on their best wishes, not only for the athletics year ahead but also her upcoming marriage to fiance Andy, expected to be in Spring 2013.
“The main things are sorted. I know the florist I’m going to be using, all the important things. And I’ll be looking for my dress this year... We haven’t sorted the photographer out yet though.”
Not a problem, because for now Ennis is spurred on only by that defining photo of disappointment in Daegu.