Life is not short. Well, usually not. I mean if you die when you're 7 or something it's short. But usually, it's long. I'll have been doing it for 51 years on 25 December, so I think I'm experienced enough to have a say.

Life Is bloody long if you ask me. I'm still doing work on visioning the next 20 years of my life, because I realised I'd reached the 20-year vision I had when I was 30. Those 20 years weren't short.

But they went quickly, looking back.

I have this theory of time, for which I have no qualification or theory to substantiate. But here it is. Time stretches into the future, but it concertinas in the past. Twenty years into the future seems long, but 20 years of the past seems short.

The problem with that language, though, is that long and short are, technically, measures of distance, not time. We know that because the short way is not always the quickest. Nor is the long way always the slowest. The relationship between time and distance is contingent on external events and internal perception.

So when people say, "Life is short," what they really mean is, "Life goes quickly." And the people who say that are usually highly motivated, productive and busy. So for them, their internal perception of time is quick, because they create lots of external events that distract them from noticing the passage of time.

But why does time seem quicker in the past yet slower looking into the future? I heard or read somewhere recently that we only remember about 20% of what happens to us (that's right, it was a YouTube video on the 80/20 rule, or Pareto principle, but I can't find it).

So, my unsubstantiated reckoning is this: When we cast our mind into the future, we imagine several scenarios of what might happen (we can only imagine what might happen in the future, because we can't predict it). We're imagining multiple versions of the future (heaps of possible external events) so that our internal perception of time slows because of considering everything that could happen.

However, when we reflect on the past, not only are we remembering just 20% of what actually happened, it is probably only 20% of what we considered could happen to us when we imagined it as the future. That's only 4% of our perceived future that we remember as the past. No wonder life seems short (but, actually, it's quick).

If you're thinking, "What about the present?" because of our current obsession with mindfulness, meditation and "being in the moment", I maintain this: The present is the nano-second in which the future becomes the past. Once you've noticed it, it's gone. (I know, that's a very "linear" concept of time, but hell, it's practical for the linear reality of our mortal existence.)

My call to action? Reconsider your belief about life. Realise that life is time not distance, and that time is not long or short, it's quick and slow. Challenge the "life is short-ers".

And if life is quick and slow, who do you want to be in that existential paradox?