You know how it is when something you have been persuaded is worth believing in goes out of the door. You know that empty feeling, the sense that the sunshine is a little less bright or that the wind which seemed to blow so invigoratingly has brought only another reason for disillusionment.
It might be held that a team of sportsmen, however young and splendid, is an unreliable vehicle for such emotion, but maybe you would believe it with a little less conviction were you here today, mourning the end of Wales' chance of winning the World Cup.
Of course, it was always possible that the French, the cynical and often too frivolous and irresolute French, would find a way to make their third final, but the worst of it is they were as disgraceful in their 9-8 victory over 14-man Wales as when they surrendered to Tonga at the end of a dishevelled pool campaign.
Wales dwarfed them in every respect, morally, physically and in their willingness to confront the most discouraging circumstances.
The decision of Irish referee Alain Rolland to dismiss the 23-year-old Welsh captain, Sam Warburton, less than 20 minutes into Saturday's semi-final has already been debated so fiercely, so angrily, that it might be a week old.
Some tell us that the official did the right thing in enforcing toughened-up regulations against "spearing" and "tipping" tackles which endanger an opponent, and the fact that it made a mockery of the competitive balance of such a vital game, that it was unleavened by a moment of reflection or consultation or assessment of intent, are of just marginal significance.
Of course such tackles are wrong. There was an element of recklessness, and potential danger, when Warburton tackled into the air the diminutive wing Vincent Clerc and then let him fall to the ground, but if he had entered a dangerous zone you knew in your bones that it was not with malicious intent and that a yellow card and a visit to the sin bin would have been appropriate.
That would have preserved one of the most important matches of the tournament but then again it might have imperilled Rolland's chances of landing next Sunday's final. The Irish referee got his decision from the revised book of the International Rugby Board and not, you had to believe, from an instinct to separate a cold-blooded written advisory from the motivations and consequences of live action. No, there is not the beginning of a case for a referee to abandon a moral dimension for the sake of the spectacle of a great occasion – as we were reminded at last year's World Cup final of football in Johannesburg, when the referee feebly abdicated in the face of the brutality of the Netherlands' attempts to curb the brilliance of Spain – but there is a duty to draw a line between the calculatedly vicious and the happenchance of a physical team game.
There is no hardship in going along with the belief of Welsh coach Warren Gatland that his young captain was due a temporary visit to the sidelines rather than permanent exclusion from a tournament to which he had brought passion and inspiration.
The Welsh are missed now so acutely because quite simply they came to play to the very limits of their ability and in a way that shamed not only their eventual conquerors – if we can make free with that particular description – but also an England team that did not begin to deliver any of the great potential we were told it possessed.
Wales, even in the moments of their defeat, roared their contempt for such a fate. For Warburton there was no limit to his misery. One moment he was at the heart of the battle, the next he was an onlooker.
What he saw only intensified the pain of his ejection. It was rugby suffused with passion and power that came so close to upsetting the disadvantage imposed so quickly.
The French were battered and harried and refused to come out of their bunker. They kicked three penalty goals and they waited for the young Welshmen to crash and burn. Their problem, though, was the crash didn't come, which meant that survival in the end was due to the failure of James Hook to land two penalties, to the Stephen Jones conversion attempt that hit a post after Mike Phillips' dash to the line (left) and the heart-wrenching failure of Leigh Halfpenny to dredge another metre or two from his long penalty-kick near the end. According to the fact, Wales were a man down. According to a deeper reality, they were a legion.