'Next!'... 'Next!!'.... 'NEXT!!!' I was jolted from my reverie, partly by the sheer volume of the yelling, but also by the fact that six or seven strangers were, by this point, all staring at me with a mixture of pity and contempt.
Oh, no - I'd become 'that bloke'; the one who's so wrapped up in his own thoughts that he's failed to notice that a cashier has become free, even though it's quite clearly his turn to plonk his basket by the till. To be fair, the girl with a voice like a foghorn was very nice to me once the popping veins in her forehead had subsided to an aesthetically acceptable level. Far nicer than I deserved, that's for sure. That'll teach me to be judgmental.
The thing is, I've always been the first to roll my eyes at 'that bloke' on other occasions. Can't he see three feet in front of his face? Has he no sympathy for the poor cashier? What on earth can he be thinking about that's so important that he loses all sense of time and space? Well, now that man was me. Where will it all end?
Once you show signs of becoming the type of person you've previously scorned, there's no telling where you'll wind up. Crumbs, next thing you know, I'll be found in cinemas talking throughout the film or riding a bicycle through a crowded pedestrian area or letting my dog jump all over other people saying 'It's alright he doesn't bite' as if that's going to pay the dry-cleaning costs.
The possibilities are quite frightening. I might strike up conversations (soon to morph into a monologue) with strangers in bars and fail to notice their body language screaming 'Leave me alone!' until they're obliged to scarper for the sake of their own sanity. Worse, I could easily be found in Malaga city centre shouting loudly in English to my chums across the street as the locals stroll by in their Sunday best, looking vaguely bewildered. Blimey, any minute now I may even get on a bus or train and start braying into my mobile phone for the duration of the entire journey.
This has to be nipped in the bud. Tomorrow, I'm returning to the same supermarket in order to buy ten items separately, thus queueing ten different times for the till and, each time, moving smartly forward to pay when it's my turn without having to be prompted.
So, if you're out shopping tomorrow and you see someone waiting in line, jogging on the spot and staring at the cashier like a stalker with a stopwatch in his hand, that will be me - making sure the rot doesn't set in.