Why am I not Prime Minister, I was thinking. How could I have let my political career drift so?

Ithink I have detected the first signs of a feel-bad factor following the Labour election victory. I say "think", but actually there's no doubt in my own case. It first kicked in on the weekend following the result, though I had noticed some early twinges while watching the footage of the Blair family arriving at 10 Downing Street, surrounded by jubilant faces and Union Jacks. And what I felt looking at this scene, buried somewhere beneath the sense of hope and the excitement of other people's excitement, was a whisper of private dismay: "Why am I not Prime Minister?" I was thinking. How could I have let my political career drift so? Of course, I should have taken heart from the fact that I had neglected to launch it in the first place (indeed, I hadn't even got round to buying a pair of deck shoes), but then that in itself suddenly seemed a regrettable miscalculation, one that was rather too late to correct. (Whatever happens at the next election, it is unlikely to be distinguished by the number of first-time Labour MPs it introduces to the House.) And though the feeling must have been worse for those who had more solid credentials for envy (in one of the few endearing things he has ever said, John Redwood confessed that he couldn't even bear to look at the coverage), you didn't need to be a politician to feel a little left behind.

This feeling got worse over the weekend, peaking on Sunday after a long trawl through the papers, which were stuffed from cover to cover with the excited responses of new members, thrilled to find they were part of the cup-winners' team. That first Sunday was a day of fast-moving weather, with passages of bright sunshine giving way to unexpected clouds - and that seemed exactly right somehow, a reflection of the odd, mixed mood induced by the election, with the landscape at one moment shining and at the next suddenly dulled, as if a low cloud had scudded across the sun.

This wasn't, I should make it clear, anything to do with political second- thoughts: the charm of transformation hasn't palled yet and the starburst of the Tory party, exploding as if in celebration, still hangs in the sky to divert us (Look! There goes Ann Widdecombe, spiralling down into a distant garden with an eerie shriek). Nor was it just a champagne hangover, the crapulous realisation that all that effervescence would inevitably go flat; Labour's first week in office kept the corks popping, each day bringing another confirmation that things really were going to change, whatever the consequences might be.

I'm afraid the melancholy was less reputable than that - an inflammation of the ambition glands that had very little to do with political affiliations and everything to do with the tick of the clock, suddenly loud in one's ears. I hope that this doesn't afflict the young in quite the same way, but for quite a few people of the Prime Minister's generation, his precocious triumph will have brought forward mid-life crises that were not scheduled for a few years yet. There has been such a surfeit of youthful success in the past few weeks (Michael Jackson's Blairite progress to the supremacy at Channel 4 hasn't exactly helped either) that it has been virtually impossible not to run a quick progress check on one's own life, and even if you had taken your contentment for granted, you would be likely to feel mildly wistful at the spectacle of such rapid upward propulsion, and wonder a little about the road not travelled. Whoever noted that we are all capable of bearing the misfortunes of others left the corollary unstated -that it is a strong man who doesn't buckle a little under the weight of other people's success

I can think of only two consolations for this mild dejection. One is that it simply will not last. "Missing the boat" may be a cliche, but it is an unimprovable one in the exactitude with which it captures the slow but dependable fading of disappointment. At first you pace restlessly on the dock and stare at the departing vessel, distracted by fantasies in which it turns back or you bribe the harbour master to ferry you out in the pilot boat. And while it remains on this side of the horizon, it is very difficult not to keep turning for another look at its diminishing form, imagining what it would feel like to be on board. Eventually, though, the last wisp of smoke has gone and you discover that the port might have its attractions after all. It helps at such times to remember Eliot's line from The Family Reunion: success, he wrote, is "what we can make of the mess we have made of things".

The second consolation is that you can never be entirely sure what lies over the horizon yourself, however dull and featureless the prospect. Only a few years ago, I have it on good authority, a well-known public figure suffered an attack of self-doubt of exactly the kind that the Labour landslide will have induced in many. He had trained as a lawyer before changing his career and now the colleagues he had left behind were beginning to take silk and advance towards high honours. To salt the wound, he felt he was trapped in a career doldrums himself, no hint of an imminent breeze and no obvious route to better things. He even contemplated cutting his losses entirely and returning to the law. Maybe he didn't really mean it - maybe this was just the sort of chest-clearing we all indulge in at low points - but whatever the case he will, no doubt, be glad that he stayed the course for a little longer because his name was Tony Blair