Never brush your teeth if you're dressed in black. Don't trust a man whose eyebrows meet in the middle. Always put the shower curtain inside the bath. Life is forever teaching us lessons, and here's another that I learnt last week: it's impossible to be mates with celebrities.

Don't worry, a smug anecdote about my self-satisfied media life is not going to follow. My existence is as pathetic and meaningless as ever. I was simply struck by the realisation when I watched a movie, spotted someone who I used to know well acting in it, and realised that we hadn't talked in years. Given the growth of the media, the sheer number of reality TV stars and tabloid freak shows marauding our streets, this will happen to everyone eventually, and most will arrive at the same conclusion as me.

Why? Well, before I explain, let me address one thing that it has nothing to do with: envy. It seems compulsory in articles on this theme to cite the lyrics to Morrissey's We Hate It When Our Friends Become Successful, but I would say that success becomes a problem only between pals who work in the same field. If you have always wanted to make it in the sphere of, say, 10m air pistol shooting, and suddenly your mate is competing in that very discipline at the Beijing Olympics while you're stuck in Tipton taking potshots at used cans of condensed milk, then I imagine that it will come between you. But if he makes it as, perhaps, a trombonist, you will be OK.

Frankly, there are bigger reasons why celebs and non-celebs can't mix, and one is that celebrity negates a major ingredient of normal friendship: banter. You may have noticed that one of the main ways in which male friends communicate is through the medium of insult. You find someone's weak point - a big bottom, flappy ears, a flappy bottom, big ears - and tease him about it relentlessly. For many blokes, it's an antidote to the relationships they have with women, where they are required to proffer constant praise and reassurance.

However, the problem with famous friends is that their celebrity blunts your ability to insult them. The satisfaction of repeatedly telling someone that he is a loser fades when he is forever being approached by strangers remarking: “I think you're fantastic. Can I have your autograph?”

A female friend of mine suffered a version of this when she dated an acclaimed comedian. She'd be walking down the street, arguing with him about where to go on holiday, or how he didn't talk about his feelings enough - the kind of bickering that seems to be a compulsory ingredient of heterosexual relationships - but would constantly be interrupted by attractive strangers exclaiming: “Are you wotsisname?” and “I love you!” How could anyone maintain their appeal in that context?

And then there is the sickening irresistibility of celebrity itself: the fact that, no matter how much you think you're oblivious to it, you end up mesmerised. The best description of the phenomenon is to be found in Feel, the biography of Robbie Williams by Chris Heath, who spent almost two years with his subject, and lists countless seemingly well-balanced individuals who attempted to form normal friendships with Robbie, but who invariably went crazy in the process of trying to do so - like Gollum with The Ring.

Perhaps the single most devastating statement on the subject, though, was uttered by Ted Beckham, Becks's dad, who recently remarked to the News of the World: “Believe it or not, I do get star-struck by my own son. It's a weird feeling. You think, ‘Oh it's my son', and then you think, ‘He's a superstar!'” If celebrity can warp even the parental bond, what chance have friendships got of surviving unscathed?

Especially when you have the additional problem of “too much perspective”. There's an analogy here to be made with illness. I once had a near-death experience (I contracted a brain parasite after eating a pork dish abroad), and when I recovered I told myself that I would never again be ungrateful for anything. I would live each day like it was my last, appreciate every person, every opportunity, every spreadsheet that came my way. But within a week I was kicking vending machines and whining about printer jams as usual.

The fact is, the longest anyone can sustain perspective is ten hours: we all have to moan about our day-to-day lives, whether we are vagrants or Shirley Bassey. The challenge for celebs is that when there's a non-celeb around, they feel obliged to put a lid on it. They can't complain about that less-than-perfect five-star hotel room or “only” getting £1 million for the next movie, because they risk being labelled spoilt or obscene in doing so.

But all privilege is relative; we're all better off than someone else. I imagine that it is quite irritating if you're not being paid as much as your co-star, or your suite at Claridges isn't quite up to scratch, and, actually, you should feel free to whine. This is why, eventually, most celebrities give up on normal mates and end up hanging out with each other.

On reflection, this celebrity apartheid is the best solution for all concerned. Everyone makes their way through life with a sneaking suspicion that other people are having a more glamorous and fun time, and celebrity mates are a constant and rather grating reminder that yes, they really are.

sathnam@thetimes.co.uk

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