However vaguely, most of us like to imagine we have some idea of what makes these paragons tick - these supermen, the likes of Roger Federer or Tiger Woods, who bestride their different walks of sporting life. We think in terms of drive, intuition, discipline, as though it were all a matter of degree. But the most relentless champion in the history of jump racing soon reduces all that to hopeless froth.
"Tiger will never be happy, never get what he wants," Tony McCoy says. "And it's the same with riding, in a sense. You live in constant fear of failure. When you've got to the top of your profession, the only way it can go is for someone to come and knock you off it. There's no other way but down. So you live in that fear every day."
McCoy remains helplessly addicted to success. Yet the jockey who will next month collect his 13th consecutive title has always conducted himself with humility, decency and integrity. Perhaps this is because perfect fulfilment reveals itself as unattainable only when glimpsed close up. For Woods or Federer, after all, to reach mankind's limits is to be reminded of your own.
McCoy reckons that Michael Schumacher never had an ego - not, at any rate, in the coarse, preening sense most of us would understand. "Because Schumacher's perception was: 'If it means killing myself, and someone else - if that means him not beating me, then that's the way it's going to have to be.' If he's got to have an unmerciful crash, with someone else going with him, because he can't beat them, then I can totally see his point of view."
McCoy pauses, perhaps himself startled by the admission. "It is a sad way to think. That you would practically risk your life, rather than have someone else get past you. It doesn't enter [Schumacher's] head, the fact that he might die. It's the fact someone might beat him. It's a bigger fear, not winning, than killing yourself not letting someone else past.
"That's what keeps you from thinking you're good. That's what makes you want to try to get better all the time. In case someone else gets better. If it means letting them win, or maybe you can stop them getting past, and you might die: what's your option? You'll take the risk. If it means stopping them, fair enough. I don't mean that's the way you ride a racehorse. But I can see where he's coming from."
Nowhere is this paradox - the fragile margin between self-belief and desperation - expressed better for McCoy than Aintree. On Saturday, he hopes to redress the one, abiding omission in that epoch-making CV. Much as when Frankie Dettori finally nailed the Derby last summer, McCoy approaches the Grand National with a festering sense of unfinished business. A month short of his 34th birthday, he knows he will not get too many more chances. Yet at least two of his dozen previous attempts would seem to offer him total absolution.
Three years ago, Clan Royal was in a clear lead when brought down by a loose horse at Becher's second time. It was a defining Aintree moment, when the random forces that govern the National vitiated all skill, all planning. And it had been a similar story, four years previously, when only two horses got round without mishap. Again McCoy was thrown to the ground on the second circuit, remounting Blowing Wind for a distant third.
"Whether Clan Royal could have beaten Hedgehunter, I don't know," he admits. "It would have been between the two of them. But when Blowing Wind went past the stands with a circuit to go, I could not believe for one moment that this horse was not going to win the Grand National. And then that happens. The thing is that it's very hard to get on the right horse for a Grand National. It only comes once a year, there are 40 of you, and 30 fences. That's why it was such a head-wrecker."
Sipping tea in his kitchen, the blood and thunder of Aintree seem a world away. It seems heartless to dwell on such arbitrary misfortunes. Surely he is exasperated by this annual ritual, all this prodding and goading? But where lesser men would be defensive, chippy even, McCoy has no problem with people bringing it up every year - because they cannot ask him anything more hurtful than he asks himself.
"If I haven't won the Grand National, it's always going to be a failure in my career," he said simply. "Anyone who's been lucky enough to be very successful, in any sport, and doesn't win what is probably the biggest event of their sport, I'd like to think they would accept they've failed. Well, they have."
McCoy is retained by the Irish speculator, JP McManus, who may have four runners. At the moment he is favouring Butler's Cabin, winner of the Irish National last year. The nightmare scenario would be for one of the others to win, but McCoy will not allow anxiety to infect his performance.
"The closer you get, the more you feel it in your stomach," he said. "But once the tape goes up, it goes purely back to riding, to getting the best position, the clearest passage. The build-up is different, and you get the adrenalin rush beforehand, but once you get on a horse, it's the same as every race."
That is exactly where some would say he is wrong. Even an authentic phenomenon such as McCoy is not immune to quibbles, and over the years some have questioned his versatility on the big stage - a legacy of his years with Martin Pipe, who liked his horses ridden aggressively. Unquestionably, there are times and places that call for more subtlety. And while McCoy has demonstrated his adaptability since joining McManus, once again he resists shallow denials.
"When I started with Toby Balding, he liked you to take your time," he reflected. "I rode lots of winners doing that. Then, when the Pipe job came along, I didn't really care what people thought. It was about keeping Martin happy and doing what he wanted me to do. And at the end of the day, statistically, it worked.
"As long as it was going to get me more winners than anyone else, then if that was the way I had to ride them, that was the way I would ride. You do get aggressive, forceful. Riding horses that are fit, you have to be fit as well. So you find people thinking that is basically the best way you can ride. But every race should be ridden to suit your horse. I'd like to think I'd ride horses in different ways to get the best out of them."
Either way, he knows he has a natural foil in his great friend and rival, Ruby Walsh. Longer of leg and often stealthier of strategy, Walsh has already won the National twice. "Ruby is a fantastic all-round jockey, a cross between Richard Dunwoody and Charlie Swan," McCoy said. "Dunwoody raised the bar more than anyone. And Charlie was a very good race rider. I went round Cheltenham, sat behind Charlie, thinking: 'Hell, how far back can you be?' But mostly he'd get there.
"Ruby and I are very different in build, even though we're similar in height. He's luckier than me, in that he's narrower, naturally lighter. He doesn't wake up in the morning and worry about what weight he'll be."
Walsh is a regular guest in the Lambourn house McCoy shares with his wife, Chanelle, and their baby daughter, Eve. Predictably, McCoy insists that new responsibilities have not magnified the perils and privations of his calling. Eve was only weeks old when McCoy was crushed at Warwick in January, fracturing two vertebrae. Yet he was back in time for Cheltenham last month, showing himself as hardy - some would say foolhardy - as ever.
"I've always been prepared to get injured," he said. "It's not something that bothers me. I know it's going to happen. You can't ride in races and not take chances. You have to take risks and if you do, you're going to get injured.
"Before I hit the ground, I always think: 'I have to get up'. From the moment I feel the horse crumbling beneath me, even if I'm in front and there's 20 behind me, I have it in my head that I will get up - no matter how bad a kicking I get. You have to think you're unbreakable. The amount of injuries I've had, it's obvious I'm not. But you go down with the opinion that you will get up, whatever happens. You brace your body for the most unmerciful kicking. If it happens, it happens. If it doesn't, you think: 'Blimey, how did I get away with that?'"
Though McCoy protests that a reputation for unusual toughness is purely a matter of profile, he concedes that he has more incentive than most to hasten his return. "There's a good chance I'll be missing winners, by just waiting for myself to get better, rather than trying to make myself get better," he said. "But lots of lads I know are every bit as tough as I am. Dunwoody never really had a sense of danger. He was someone who could never lose his bottle, because it just never even entered his head. It's totally a mental thing. When I get on a horse I don't think of anything, only trying to win."
Again, that gluttony for success, come what may. And the mystery persists: how can he be so pitiless in his addiction, and yet so free of arrogance? He quickly notes that his upbringing would never have nourished egotism, whether at home or at work. "Especially with Jim Bolger," he grinned. "I don't think there was ever much chance of getting an opinion about yourself there. I started arguing with Jim one day, and he said: 'I tell you one thing: never start an argument unless you're right. And when you're arguing with me, you'll never be right. Now go away.' The problem being that he always had an answer for everything. But if I was to do it all again, I could think of no better people to work for."
Horses are themselves a great help when it comes to keeping your feet on the ground, because if not your feet, it will be your backside, or even your head. Yet that clearly weighs little with McCoy. The fact is that a sense of invulnerability can only relate to the past. By always looking forward, you break the chains of vainglory. As McCoy says with a shrug, he remains "more worried about what's going to happen tomorrow than what's happened yesterday".
And he does worry, truly he does. A few years ago, he could pick and choose rides whenever Pipe did not need him. Nowadays the same trainers have their own jockeys. And the sudden supremacy of Paul Nicholls's stable has changed the landscape altogether.
For all the familiar pallor of those long, gaunt features, there is not the faintest hint of decline in McCoy's riding, and nor would you expect any for a few years yet. As and when it happens, however, he will react before anyone else. Once again, he addresses the prospect starkly.
"How am I going to know?" he said. "I'll tell you how I'm going to know. It's pretty simple. This year has been [one of] my worst ever, as far as number of winners is concerned. And if it kept getting worse, then that would be it. I know I was injured at the busiest time of the season. But it definitely has to be better next year. Definitely."
But surely he must be comforted that nobody, during his absence, remotely menaced the top of the table? "I'm not worried about what anyone else is doing," he said. "It's about my own peace of mind. No matter how much I love riding, if I couldn't be as competitive as I had been . . . It wouldn't matter what they said. 'You still look like you're riding well.' I don't believe in that shit. I'm not one that could suddenly start to fall down. That wouldn't be me. I couldn't cope with that mentally. I'd rather sweep the road."
McCoy's life and times
*Anthony Peter 'AP' McCoy MBE
Born 4 May 1974 Moneyglass, Co. Antrim
*First winner: Legal Steps, at Thurles, 26 March 1992
*First winner in Britain: Chickabiddy, at Exeter, 7 September 1994
*Champion conditional jockey: 1994-95 with 74 winners - a record by a conditional.
*Champion jockey: 12 times, commencing in 1995-96 season.
*Records broken: Fastest jockey to reach 1,000 winner mark.
Winners in a season for all types of racing 289 (beating Sir Gordon Richards's record of 269 on 2 April 2002)
*Grand National failures
1995 Chatam (fell 12th)
1996 Deep Bramble (pulled up two fences out)
1997 Unable to ride
1998 Challenger Du Luc (fell 1st)
1999 Eudipe (fell 22nd)
2000 Dark Stranger (unseated 3rd)
2001 Blowing Wind 3rd
2002 Blowing Wind 3rd
2003 Iris Bleu (pulled up before 16th)
2004 Jurancon II (fell 4th)
2005 Clan Royal (carried out 22nd)
2006 Clan Royal 3rd
2007 L'Ami 10th