"IT WAS my fate, my destiny, to be a fan," wrote Frederick Exley in A Fan's Notes. It is the same for most people in the world. The realisation that you are never going to run out at Old Trafford or lead the field going into the final bend of an Olympic 1,500 metres final is one that dawns on most of us at a cruelly young age. Even relatively talented athletes and sportspeople bow out of their chosen games with accomplishments that are comically modest in the grand scheme of things. It doesn't help either that the goalposts keep shifting: God knows how many people have run the sub-four mile since Roger Bannister but they won't replace the good doctor.

The peculiar thing is that the less one actually achieves on the field, the more precious and vivid the rare - and perhaps accidental - instances of personal triumph (the substitute appearance and point in the Hogan Cup semi-final of '82, the winning goal in the Metropolitan Wednesday Night Indoor Soccer Men's D final 1977, the sub-four hour London marathon in 1990, the reserve game in which you swear you got booked for "tangling" with Brian Mullins) can seem.

That is as it should be. When you meet the transcendent sports stars, the few who have left a glittering trail of record-breaking accomplishment in their wake, they are often vague and frankly impatient about recalling the details of their success. Compiling dossiers of their brilliant moments is something - much like their kit being folded perfectly and the dressingroom made immaculate after they leave - that simply "gets done". And anyway, they know that their fans will always remember the dates and details for them.

It is a strange business, the life of a fan. Very few people get away without at least a mild hankering after one team or another. Jack Nicholson would probably have another 30 films to his credit if he wasn't such a devout LA Lakers fans. Every Saturday, Osama bin Laden is probably pointing a Roberts radio at the sky trying to tune in to the BBC World Service to hear how the Arsenal got on, a legacy from his days spent in London. Delia Smith will be Norwich until she dies. Being a fan is not a trivial business.

You know it: you probably are one. Something happens to people once they pass through the turnstile. It is a kind of full moon syndrome. People are strange, as old Jim Morrison used to sing. Not so long ago, I found myself studying one particular fan at a game I attended. The sport doesn't really matter. He was a middle-aged man and was in the company of his wife and children. Sitting in the terraces, he was all smiles and drank coffee to keep the damp chill at bay and he waved at a few faces he seemed to know in the crowd.

But after the game started and he warmed up - fans have to feel their way into a match much the same way as the stars on the field - a subtle and then dramatic change overcame him. He developed a keen and extremely loud distrust of one of the defenders on his own team, yelling "No, No," whenever the poor lad went near the ball and screaming "Take him off" at the manager on the touchline.

He quickly became obsessive too about the performance of the referee.

Every call merited a howl of indignation - when the poor man whistled for half-time, the fan let fly with a volley of denunciations on reflex.

"It's about the only call he has got right today," he said defensively.

He became tearful in the second half, branding this and that a disgrace, getting into a running argument with a man a few rows back and he let a few blood-curdling roars at nobody in particular that caused him to foam a little around the mouth. It was the kind of behaviour that, if tried in a supermarket or at the cinema, would merit instant arrest or the arrival of men in white coats.

Here, nobody played a blind bit of notice - one of his daughters gave him the odd pat on the back, the way you might humour a pup seeking attention. And all of this even though his team was winning - comfortably.

After the final whistle went, he was the picture of contentment, courteously insisting on ladies first down the steps and was clapping his hands like a man anticipating a heartily good meal. You never worry about those type of fans. They get rid of all the angst and are ready for a new week.

It is the silent ones, those that study the action with their hands in their pockets, biting their lips and gravely concentrating on the game, their faces unreadable whether their team is winning or floundering; these are the guys that we fear about, bottling it all up, season after season. Sooner or later, they are going to have to flip.

Because it is a high-pressure passion, following a team. We have all heard the Saturday afternoon radio phone-in shows where anonymous Irishmen - "Pat from Kerry" doesn't give too much away - turn morose and confessional as they open up about their feelings about Roy Keane or whether Fabregas is all he is cracked up to be.

Not so long ago, one man phoned in to admit that he was "disillusioned" by Rafael Benitez. It was a heartfelt and moving piece of radio and you felt a burden had been lifted from him afterwards. There was nobody else he could say it too, after all. For weeks, he had been probably been mooching about the house, causing his Missus to fear he was fretting for his job or the future of their children or just blue about the country in general.

He could hardly explain to her, as she asked him for the one hundredth time, that he was actually lying awake at night worrying about a chubby, eccentric Spaniard with a half-Merseyside accent that he had never met before.

Because she would think he was mad. And the lot of a fan is to be slightly mad (As F Exley knew more than most).

There are many fans out there who have lain on the operating table and come perilously close to "the big thing" - they have seen the white light and felt the extraordinary peace - only for some whiz kid surgeon to pull them back from the brink, save their life and present them with a bill for 80,000 quid. But despite having gone through this phenomenal experience the fan will, after coming around, sit up and demand to know how Everton got on in the derby or what that pup Brolly had said on The Sunday Game.

And fans who are told, after particularly serious operations, that they should not attend games for a few months - on the grounds that their notoriously wild behaviour is liable to kill them - will sulk at the news. They will feel the world is conspiring against them and complain that they would be better off being fully dead than being half alive.

Because once you pay your fare and walk through the turnstile, you can be whoever you want to be. Being among the crowd as a fan is one of the few places left in society where you can let yourself off the leash for an hour or two without any fear of retribution. And Lord knows, in these trying times, everyone deserves that much. Happy Christmas.

"He became tearful in the second half, branding this and that a disgrace, getting into a running argument with a man a few rows back and he let a few blood-curdling roars at nobody in particular . . .