A few days ago I found myself walking around the Bowie exhibition at the V&A, gawping at his prodigious output during the 1970s and bemoaning my failure to produce anything comparable during the same period. While Bowie was recording "Heroes", I was playing a goblin in a mercifully short run of a school play called Jan's Journey written by my headmaster, Mr Curtis. It's an unhelpful comparison, obviously.

Bowie was a spectacular talent reaching creative maturity, working with Eno and Fripp. I was six, working with a bunch of six-year-olds who wouldn't know dramatic irony if it was served up for lunch with chips and beans and called "dramatic irony, chips and beans".

But you can't help but make these pointless comparisons when confronted with an exhibition like this. Bowie was 24 when he wrote "Life on Mars", for chrissakes. I just thought back to when I was 24, and I think I spent most of that year worrying whether I might have new variant CJD. Brilliant.

Faced with the problematic atheist position of not knowing what the purpose of human life is, I tend instead to perform arithmetic based upon other people's achievements to work out what I ought to have done by such-and-such a year. For example, I frequently have the niggling thought that by the time my dad was my age, he already had a 12-year-old son. Me. I was getting into The Smiths at the time. In fact, "Hand in Glove" by The Smiths came out exactly 30 years ago – and if you go back another 30 years, Elvis hadn't even set foot in a recording studio!

What does this mean? Not much – but it contributes to an unsettling feeling of underachievement coupled with the seemingly rapid passing of time.

A few years ago I started avoiding reading biographies of people who'd achieved stuff at an early age, consoling myself instead with thoughts of Kenneth Williams, who wasn't in Carry on Camping until he was 43, or Mother Teresa, who didn't bag the Nobel Prize until she was 69.

So there's still hope, right? I still have time to appear in a bawdy British comedy, surely, or perhaps set up an orphanage, I think to myself, as I slump on the sofa on a Sunday, stuffing some Pringles into my face because there's nothing else to do.