It was the point at which I was telling a colleague that the prospect of a two-run weekend (with a 10k race instead of a Sunday lie in) was deeply exciting that I realised just how much my life has changed - and how one-note my chat has become!
Then I realised, it's not just the chat that's changed. Training for a marathon affects far more than your choice of conversation topic or your weekly schedule.
I feel that I owe it to all first-time marathon runners out there to confess the what and the why so that, at best, they don't feel alone as they adopt quirky new marathon-training habits - and, at worst, they know who to call if their friends desert them.
Question is, are you brave enough to confess along with me? Here are a few of the telling signs:
1) You could give a weather forecaster a run for their money
How did I exist without the BBC weather app - on not just one, but three devices so that I am never without a fluffy white cloud or multiple rain drops? A fellow runner did advise me though that no amount of 'refreshing' the screen will change the picture. Shame! I didn't know ice skating skills were required. And, I still laugh when I find myself worrying more about my phone getting wet than my body.
2) A big night out means smelling kebab shops and smiling at runners as you train
While there is a lot to be said on the health front for running home and simply smelling restaurant food, a diary packed with training runs - not socialising with friends - takes some getting used to. I did manage a play a few weeks ago, but even found myself wondering whether or not any of the actors had taken the leap into pre-race lunges and long runs. That might say more about the play though!
3) You have unhealthy obsession with pavements
As someone who has only ever (touch wood, body please keep working) had time off running (since taking up the sport just 18 months ago) for over stretching in pilates and, unbelievably, sitting for too long in a cross-legged position, I now fear my marathon dreams will come to an end thanks to something as simple as an ill-placed pavement. That's why to watch me mount one (delicately) is a source of much amusement!
4) You wonder why M People's Proud isn't on everyone's iPod and the sound of the London Marathon music makes you a tad bit emotional
Backstreet Boys, Miley Cyrus, Girls' Aloud, The Script's Hall of Fame and M People are, yes, all on the marathon playlist. If you're pushing your body to the edge, you certainly need lyrics like 'what have you done today to make you feel proud?' and 'there's always gonna me another mountain, always gonna want to make it move' in your life - and blasting out of your earphones! Hasn't done wonders for my reputation mind.
5) You sleep in your running kit
Ok, so I haven't gone as far as the compression tights yet, but the blister-resist socks and the running knickers are a bedroom staple. By popping them on with my Eskimo-like pyjamas, I feel like I already have one foot out the door. I do also now have knickers everywhere - in the drawer at work, in my handbag, in my rucksack. You name it, I have clothes in it. Maybe the less said about this point - and my obsession with Lycra - the better.
6) You get excited when you learn a new running term
The word cadence made its way into my life last week (to add to terms like tapering and fartlek in the months before). I now know the importance of a foam roller and understand more about dynamic stretching than I could ever have imagined. Does it make me faster? No. Does it show that I can talk a good game? Absolutely!
7) You eat everything 'for added energy'
I am not sure anyone needs six carb-friendly meals a day and a helping of chocolate digestive on the side. And, maybe the second breakfast is a bit excessive. There is a reason most marathon runners don't actually lose weight even with the extra miles. And I thought there might be one perk!
8) You think everyone is interested in how far you're running
No, in truth, most people are either being polite, feeling inadequate at being reminded that couch surfing is not a sport or wishing you'd run miles in the opposite direction. After all, nobody likes you if you talk more about burning calories than you do what you're eating for dinner. And, they like you even less if you remind them about sponsorship (for Breast Cancer Care) when they have Christmas credit cards bills to settle.
9) Your life is measured in 1KM chunks
If you don't have a wearable monitoring your every move - I have a running watch, a Fitbit and three phone apps that all tell me different things - you are not a true marathon runner. There is truly nothing more exciting than hearing your wrist beep or buzz to tell you that you're one step closer to not actually having to run for the rest of the day.
So this is my public apology to the world. I am sorry for getting excited about the rain, the rather embarrassing playlist, the chocolate and carb-based diet (on top of the healthy stuff of course), the non-existent social life and the scintillating pavement chat. I am sorry if running 20 miles as part of my weekly commute is sickening to you and I am sorry if you have found a pair of my knickers in an inappropriate location.
But, I won't be quite so sorry if it gets me over one of the world's most famous finish lines in one piece.