A marathon is seen as an incredible triumph of the human spirit, taking your body to the extremes, breaking through the pain barrier, calling on every tiny grain of stamina in every fibre of your being, one of the greatest human achievements.
Definitely sums up a lot of what I have been through in the past two and a bit years.
But, alas, an analogy is just for those who don't have what it takes to do the real thing.
So Mr Trusty Companion decides he's had enough of everyone saying how great I am, what a hero I am, how brave I am, what a fighter I am. (Do people say this? They flipping better.)
He's going to go and run the ridiculous-point-demented number of miles, and he's going to do it for a cancer charity. Way to outdo me there buddy.
The least I can do is be as supportive to him as he has been to me.
Washing the extra shorts/socks/t shirts. Entertaining the children every Saturday morning. Being woken at 6:30 by the sound of the running jacket being zipped up, shortly followed by the sound of rampaging hungry children.
We'll be there at the sidelines with the bananas and Snickers. We will cheer loudly at the half-way point and try not to be disappointed when he doesn't see us in the crowd. We will barge our way through the seething masses to not-hug his sweaty and aching body.
On my first day in the chemo ward I was given a large pile of Macmillan information leaflets. I kept them next to my bed for the next three months, and other than one brief, terrifying internet search at 3am one morning, looked nowhere else for information about my treatment. Effects, side effects, what to do when various horrific nastinesses befell me. All of this was contained in the by now grubby well-worn photocopied sheets.
This is what Macmillan did for us. A safety blanket for the bewildered.
So that is why we will be cheering on the lunacy on April 9th.
(And praying that he goes back to the half-marathons again. Far more civilised.)
And for once I really will be saying that it is him I feel sorry for.
(If you'd like to support him, or Macmillan, then here's the link. He's already got loads of sponsorhsip though, and if he gets much more he really will be outshining me. And we can't have that.)