I also have to make a shopping list or I will forget the very thing I went for.
Tell me about it. I'm guilty of this one more often than I care to imagine. And now I have another little story to tell.
I had to run some errands today, one of which was stopping at the supermarket for one specific thing, and anything else I thought of while there would be fine. After reading your post I very nearly made that list re those errands -- but I knew, due to the nature of them (blah blah blah) that I wouldn't forget anything. Right?
So, I was nearly done picking up the dozen (yes, it had become a dozen) items at the store and was ready to start moseying toward the cash registers when I suddenly remembered: the THING. It had become the last thing I thought of, and was very nearly forgotten. Thanking the gods and tipping my hat in the direction of DR Jrand65's post, I picked up the item in question.
(I can hear you all wondering what it was. It was a jar of horseradish sauce.)
Anyway, I then ran the other couple of errands, planning to fill up the gas can (for lawn mower, etc.) last. I decided, however, to make one additional stop, and as I finally turned into my driveway I looked down at the BIG RED GAS CAN -- and what issued from my lips will not be repeated here.
It's three miles, one way, to the nearest gas station, and I could have just said 'oh, well...' and put that off till tomorrow. But I was so furious with myself I decided I'd best learn my lesson by turning around and going back out to get it.
BTW, my usual mistake is intending to fill a gas can but forgetting to put one in the car. So you see, you can't win.