My colleague Jon, his knee still unsteady after surgery, refused to play golf this week at a corporate event. He offered the Tiger Woods excuse. He said his game felt "vulnerable". No one, I reassured him, was going to judge him - unlike the millions for Woods - and yet he was fearful. Faith had taken flight and it was sweet and tragic.

Woods, the athlete who showed the world, now cannot bear to show up before the world. A hero in a moth-eaten cape. Now he and Jon find themselves confronted by an ancient truth: There is no greater search in sport than for confidence, yet no greater guarantee that once found it will eventually leave.

At its best, confidence is like a perfume which is probably why we can never hold onto it (clearly the makers of the perfume Unlimited Confidence never played sport). You can see it arrive in Angelique Kerber's strong body language but also see it slightly fade in the choice of Rafael Nadal's words. His forehand used to be Indiana Jones' whip and yet last week he admitted, "I need to recover my forehand". When an aura alters, so does a vocabulary.

Every athlete will feel empathy for Woods and Nadal, for confidence is our collective umbilical cord. Doesn't matter who you are, said Wayne Gretzky, the legendary ice hockey player, "confidence is everything". Even amateurs know the feeling. For that brief, rare game on a weekend when second serves are hit with authority and trust, life feels splendid.

Confidence, says Dr Andrea Furst, a sport and exercise psychologist who works with Great Britain Women's Hockey, "has one of the strongest relationships with sporting success". When it's gone, professional shooters hesitate in pulling the trigger; when it's there, every envelope of possibility can be pushed.

"Confidence," said high diver Gary Hunt to Fina magazine, allowed him to leap off cliffs. Similar magical flights were designed by Woods. He'd send a ball 190 yards, through branches, over lakes, soaring on his self-belief all the way to the pin. He'd have that look about him, perhaps the same thing in smaller measure that Roberto Bautista Agut sees in Andy Murray's eyes. A glint of assurance? It has gone from Novak Djokovic.

Confidence can be discovered in the feel of a golf putter, in the inspired words of a coach - Real Madrid's Isco insists he gets it from Zinedine Zidane - and in the sheer grind of dogged labour.

As Furst, the founding member of Mental Notes Consulting, pointedly says, "a key source of confidence is training" and Woods she knows was a relentless worker on the range and the course. From practice is built instinct, from sweat arrives certainty. But Woods' back and knees have been surgically repaired and as Furst adds, "I would imagine he hasn't been able to do (extensive practice) in a very long time".

Confidence feeds and fattens on victory but, with no win since 2013, Woods is starved of self-belief. Confidence is also drawn not just from physical condition but also, says Furst, "from physical presence".

Woods' physicality, his wide shoulders and muscled arms, seemed to send messages to himself and warnings to his rivals. It reinforced a sense of indestructibility but now, older, his body less obedient, perhaps it has been stripped away. In the mirror, no self-possessed god is reflected back at him.

Now and then, something shrinks within creative people and occasionally deflates their genius. Years ago The New Yorker published a piece on writer's block which began with the example of Samuel Taylor Coleridge. Most of the poet's memorable works, they noted, were produced in his mid-20s and thereafter any "ambitious writing project inspired in him what he called 'an indefinite indescribable Terror'."

Perhaps this is where Woods is now, his mind flooded by a river of urgent questions: Can I win? Can I withstand the yips? Can I give up that stare and silence and win by being nice and relaxed? Can my body last? Can I bear to be average?

You might think it just, or ironic, that even sport's billion-dollar man cannot buy what he most needs. But there is no pleasure to be found here. After all, it doesn't matter how many times we see it, it's always awkward and strangely depressing when the extraordinary athlete misplaces his confidence. He looks human. Like Jon. Like everyone else. But we preferred it when he wasn't like anyone else.