I was at the supermarket earlier today buying yogurt. It was on sale, with a digital coupon, it's my favorite brand, it usually costs more than I'm willing to pay for a cup of yogurt, and it's one of the few yogurt brands guaranteed to be gluten free. So I got the maximum possible allowed under the terms of the sale and the coupon.

This old lady in a cart was at the next self-checkout (partially blocking mine, but I could deal with it) with I assume her daughter. She watched me ringing up the yogurt, then said, "How much yogurt are you going to get?" I said, "as many as the coupon allows."

She watched me a bit more. Then she said, "Are you going to eat all that yogurt yourself?" I just ignored her. She was already being rude. I could tell it bothered it to be ignored, but I just kept on doing it. And finally she moved out of my way.

I think this is my future approach: ignore rude questions from strangers instead of trying to be polite. It felt very satisfying.