I do my family's grocery shopping online, at a large and well-known supermarket chain. I don't want to give them free advertising, so let's call them "Fresco".

The way the kosher section of their website works has been a bit odd recently. Every time I tried to buy Shabbat candles, I got a message saying, "Sorry, this product is currently not available. Why not try kosher baked beans?"

This went on for several weeks, until finally I noticed that the problem had been fixed. With searing psychological insight into their Jewish customers' shopping needs, they were now recommending I try a different brand of Shabbat candles.

I thought all was well until I scrolled down to the next item: Memorial Light in Glass:

'Sorry, this product is currently not available,' read the message. 'Why not try Gefen Chicken Ramen Noodles?' …

If I actually went into the store I would avoid this sort of problem. Unfortunately, when I do so, I seem to encounter all sorts of other difficulties.

A while ago, for example, I was in the fresh produce section at my nearby branch. I'm completely hopeless at opening those fiddly plastic bags they provide for fruit and vegetables: I can spend the best part of a day forlornly rubbing them between my fingers to no avail, with an occasional diversion where I try to get my nails into the gap and prise them apart.

So having selected some broccoli, I was pleased when I spotted an already-open plastic bag lying next to it. It wasn't one of the bags meant for customers - it had clearly contained vegetables before they were put out on the shelf. I popped the broccoli in it and thought no more about it. Until I got to the checkout.

It turned out that the bag I'd picked up had a label on it saying "cauliflower". The lady at the till read the label suspiciously, then took out the broccoli, held it up and said: "This is broccoli."

Me: "Yes, I know."

Lady: "It isn't cauliflower."

Me: "No, it's not."

Lady: "But the label on the bag says 'cauliflower'. "

Me: "Yes, it's just a random bag that I picked up."

Lady: "But you realise this is broccoli?"

Me: "Yes, it's broccoli."

Lady: "Not cauliflower?"

Me: "No, not cauliflower."

She cast the offending bag to one side and put the broccoli in another one, then scanned the rest of my shopping, occasionally giving me suspicious glances in case I did something else equally dangerous and renegade. Meanwhile, I vowed never again to diverge from the official bagging system.

On another occasion, I was in the shop with my children. As we walked down the central aisle, one of the shelf stackers swung round suddenly, and as he did so he accidentally whacked me across the face.

Purely from the shock of it, I began to cry. I stood there sobbing really quite dramatically, while at same time, a rational bit of my brain was saying, "This doesn't even hurt that much. Why are you crying?" It seemed to be an uncontrollable physiological reaction. I simply couldn't stop.

The shop assistant, who looked like he was barely out of school, was clearly utterly appalled. He had absolutely no idea what to do. He just hovered, terrified, occasionally asking if I wanted a drink of water - to which I didn't reply because I was crying too much.

Meanwhile, my children, bored and oblivious, asked me if they could go to the next aisle to look at the toys.

"Mummy! Why aren't you answering me? Can we go and look at the toys? Mummy! CAN we?"

Rather than a crying adult, a more usual supermarket scenario is to have a screaming baby in your trolley or a tantrumming toddler. Parents speak of the stress of enduring not only the hideous noise their child is making, but the hints and tips - well meaning or not - given by other customers. "Ooh I think he's tired, poor little chap." "Don't you think those feet are cold without any socks on?" …

The first time this happened to me, I was pushing my pram round the store, the sides practically shaking with my baby's howls of rage. An old lady came marching up, purposefully.

"Here we go," I thought, bracing myself for criticsm or advice as she peered into the pram.

Then she looked up at me, gimlet eyed, and said, "He must be very intelligent."

I have loved that old lady ever since.

@susanreuben