I had the thought of this post a long time ago, but just now got to it because I was cleaning up the backend of our blog. In the US, you never have to give any thought to how many groceries you buy or what you get in the store. Here it's always on my mind when I'm shopping.
I know I have to walk at least 3 or 4 blocks to the closest store so buying too much could mean torture for my hands and shoulders. Especially if you forget your gloves on a cold, winter day or can't use your umbrella in a rainstorm because of your bag choice. Those two situations make it sound unpleasant.
Most of the time it's nice to go shopping every few days instead of once every week or two because 1) the stores are much smaller than the ones in the US, 2) you don't have as many choices so you just pick and get on with your life rather than agonizing for hours over what brand of milk your husband likes best, and 3) it's one of the ways I feel active during the day. Plus walking home through the quiet streets of our neighborhood usually means I'll bump into a neighbor or see a cute dog along the way.
I still have to remind myself sometimes that I don't need to buy the whole store. I think it's an instinct I carried over from the US. I hope I can keep it up when we eventually move back to the US.