20 miles and the question of 6.2 more seems insurmountable. Nevertheless, you persisted.

It feels like a shuffle, but it's movement. Painful elation. Nevertheless...

It was, maybe, the crowd, so deep and loud – and you so visible that you'd be instantly pressed to get moving – that you daren't stop.

On the Embankment now, three to go. 23 done? In reality, many more miles are behind you; not just a couple of hours into this race, but weeks, months. Consuming your entire personality. Defining you, from future tense: "I am running the London Marathon" to now, the present tense "I am running the London Marathon".

Big Ben, Birdcage Walk, Buckingham Palace, The Mall... the finish has never seemed so far away. Painful, painful elation. The finish line crossed, the metaphysical line into another realm crossed many miles ago. 14 to 16 weeks of training and preparing suddenly done.

Soak it in, wear the medal. A blur of celebration reminiscent of seeing through the hazy morning hanging over the London roads in Greenwich before the start.

And suddenly it's Monday morning. The traffic is back on the Embankment. Tourists taking selfies on Tower Bridge. Like nothing ever happened yesterday. Just the excruciating soreness that you feel individually alongside 56,000 others.

Now that the dust has settled, what the hell do you do now? An entire facet of your life wiped away. The joy of completion masked by your inability to roll out of bed without each fibre of your being screaming for help. Thank god you don't have to run again anytime soon.

Oh, yikes, I don't have to run. No more checking your running plan. Buffets of gels and drinks no longer a fixture of the kitchen counter. It's a funny thing, going from elation to emptiness in such a short period of time, like something has been taken away from you which at you couldn't wait to be rid of, but now you miss.

Maybe there'll be another in the future, maybe not. But what fills the void? Embrace the rest, twiddle the thumbs, allow it to fill you like training did and realise that, hey, you didn't hate running quite as much as you thought when you were digging in for that long run 6 weeks ago and actually you kind of miss it. And now you think of it, you want more.

But take your time, fight the urge, let the dam fill the reservoir before you simply must lace up the shoes. Then, you run. Not for a goal, but for the simple pleasure of doing it. Remember how it felt to put your feet in front of each other. No noise of a crowd. But remember it.

Past tense: "I ran the London Marathon"