The point is that petty, frustrating crap like this is exactly where the work of choosing comes in. Because the traffic jams and crowded aisles and long checkout lines give me time to think, and if I don't make a conscious decision about how to think and what to pay attention to, I'm going to be pissed and miserable every time I have to food-shop, because my natural default-setting is the certainty that situations like this are really all about me, about my hungriness and my fatigue and my desire to just get home.