It's the eternal problem of youth. Those who have it don't know how just how exciting it can be. Those who no longer have it often forget what it was like to possess it.
Without acknowledging the generation gap, there can be no regeneration.
Ireland's ageing international side grew so imperceptibly old before a nation's green-tinted eyes that suddenly they were gone before they knew it.
What is left instead is a gaping hole in terms of experience and that, whatever one's opinions on how belatedly Giovanni Trapattoni has managed the transition, is the current reality facing this Ireland team.
It was a reality starkly exposed by the world-class Germans when they visited Dublin in October.
On that occasion, Ireland presented themselves in competitive football for the first time in 15 years without any representative from Ireland's supposed golden generation – Shay Given, Richard Dunne, Damien Duff and Robbie Keane.
Two of those have retired, never to return, presumably, despite awkward entreaties from a manager whose gaucheness arguably prompted them to leave in any case.
Twin Tallaght totems Dunne and Keane remain shadowed by injury and their future days in the green jersey are thinning by the hour.
The planning for this group's absence has not always been straightforward or seemingly brimful of logic.
Trapattoni, so strident in his defence of a system and a still influential coterie of senior players who, occasional sorties apart, would not challenge the manager's assumptions, has always seemed reluctant to give youth its fling unless compelled to do so.
His procrastinations were, for him, steeped in the enduring reality of the present.
After all, the Irish side that kicked off 2012 had done so on the back of a 14-game unbeaten run, which included 11 clean sheets. Such certainty precluded him from swaying him into the realms of new discovery.
Critics of this regime, who argued forcefully that an inability to sway from the tried (or tired) and trusted would be exposed against better sides, were dismissed as fantasists.
The harsh realities since then have not been pleasing to report.
But there is encouragement in the recognition from the manager that, acknowledging that one is never too old to learn new tricks, he can absorb the sudden exit of so much experience and propagate an influx of the youth he once distrusted so virulently.
Yesterday morning's training session in Lansdowne Road demonstrated the first tangible signs that this Irish team may have a much better temperament or, at the very least, a far more enhanced sense of trust placed in their hands by their manager.
Aside from the full-backs, given renewed licence to have their passports stamped beyond the white line, notwithstanding the endless toil to which Seamus Coleman was subjected against Germany, the main beneficiary could be James McCarthy.
While his – and indeed Ireland's – performance last Friday may have been over-praised in the light of a horrendous sequence of results against the world's heavy hitters, it may yet prove to be a significant milestone.
After all, this is a team striving for an evolution in style while undergoing a revolution in personnel.
And so, as Trapattoni took McCarthy and his fellow players aside before, during and after yesterday's training session, the messages he imparted will prove vital in ensuring that Ireland can maximise the potential displayed in Stockholm.
One only hopes that he proved more successful in communication than on many occasions before but the tenor of his argument appeared inescapable.
It was not simply about telling his new players how well they performed – but showing them how effectively they performed.
It was not simply about clapping them on the back and praising Friday's performance – but emphasising that they are only as good as their next game, not the last one.
"This morning before training, I congratulated them on the performance against Sweden," reported Trapattoni, gently easing into an explanation as to how confident he is about his young, inexperienced players' hastened quest for maturity.
"This morning, I showed them how they played. I showed them how their behaviour and their confidence was so important, in enabling them to begin attacking immediately against Sweden.
"So it was important for them to see what I said, not just to tell them. They have seen it demonstrated to them. Also, tomorrow, we need to see this behaviour."
At once, this was a demonstration of intent, particularly ahead of a home engagement where Irish teams under Trapattoni have not always, even with experienced players, demonstrated such positive aspirations.
"They have made a good performance but by not only knowing what they did, but seeing how they did it, this is what gives the players confidence to do the same again," Trapattoni emphasised.
This renewed emphasis is integral to the Irish challenge and one that can inculcate in Irish supporters a confidence that the team will not more withdraw into a cocoon of inhibition, one that has conceded the initiative in Dublin on so many previous occasions.
When this general process is viewed through the prism of McCarthy, in particular, one can see the potential benefits that may be harvested as Ireland seek to gain control of the race for their age-old status as the second-placed side in qualification campaigns.
Providing a literal punchline for the headline writers – noting with exasperation that he could sometimes "punch" McCarthy because he is so shy – the manager intends to cajole something extra from a midfielder whose energy could be so vital to Ireland's challenge.
"We see also against Poland that James McCarthy is a player who can be up and down in terms of his confidence but it is also true that he is technically consistent," said Trapattoni.
The key to the manager's task this week with the midfielder, as with all his relative newcomers, is to regulate that inconsistency in confidence levels.
"The personality can often be up and down but the technical ability is always there, that is important."
He namechecked Austria's Marko Arnautovic, always a player of outstanding promise but one who has historically suffered from the vicissitudes of vacillating confidence levels.
There are still vital pockets of experience in this side; Glenn Whelan's introduction in midfield will be a crucial factor here.
So too John O'Shea's captaincy from the heart of defence – his "confidence" and "personality" were clearly evident in Stockholm.
But tonight will be all about Ireland's youth. Ignored for too long, many of them, it is true.
But now that the manager has finally embraced their ability, he has also encouraged their personality.
Presuming the manager does not lose his nerve, Ireland's players now have to prove they can keep theirs.
And in doing so, solve the manager's youthful dilemma by simply helping him to express his faith in it.