When I turned 21, a well-wisher told me: “Remember, you are 21 only once.” He might have said the same to me (correcting for age), when I turned five or 13 or 42 He didn’t. There is something about someone turning 21 that brings out the sage in the rest of us. We advise, we say things that would sound silly under other circumstances, we hope to sound profound and deeply philosophical.

Depending on my mood, I usually tell the 21-year-old, “the best part of your life is over” or, “the best part of your life lies ahead.” Sometimes I combine the two and say, “the best part of your life which lies ahead is over.”

I have often wanted to give a one-word advice like the character in The Graduate who told Dustin Hoffman, “Plastics.” I would like to say, “Chair” or “Magnitude”, and walk away. There is much joy in confusing a 21-year-old.

Those of you who were bouncy ten-year-olds when this magazine was born are 31 now, at the peak of your careers, and probably bouncing still. Depressingly, anyone over 18 was born in the last century. Unlike magazines which have to get sharper and eliminate all errors as they grow, human beings get duller and become more error-prone.

Research has shown (Ah, those three magic words that justify everything) that as you age, your bones weaken and the hearing goes, but your sense of humour actually improves. At four it is enough if you are shown the visual of someone slipping on a banana peel. It entertains you for hours, even days as you keep recalling it.

At 21, that is no longer sufficient. Now you need clever wordplay or situational comedy or your worst enemy falling and breaking his neck. This last is a guaranteed smile-raiser, if not a laugh riot. Psychologists aren’t telling, but perhaps an improved sense of humour merely means greater tolerance.

I am often asked (well, not really, but let’s pretend you asked) what advice I might have for my 21-year-old self. Here goes:

1. You are not the cock of the walk, monarch of all you survey or the cat’s whiskers. But live as if you were.

2. Always watch the other person’s knees. They will tell you when he is about to take a swing at you (Excellent advice from P G Wodehouse).

3. Don’t believe money isn’t important.

4. Don’t believe love isn’t important.

5. Learn to distinguish between love for money and love for love.

Dear Friday, I remember the day you were born, when you turned one, ten and 18. I have only one thing to say to you now: Remember you are 21 only once.