I feel this. One time I was out shopping with my then wife, and I noticed an old (like 70) man struggling to figure out what coffee to buy. I wen't over to himand asked if I could help him find anything. He said he needed to find decaf for his wife, but couldn't tell which ones were decaf. I looked through the aisle with him and pointed out the decaf version, and tried to give a little description of each. He eventually settled on one and went on his way. As I walked back to my wife, I could see the admiration in her eyes, she thought I was so nice for that gesture. So of course I had to mutter under my breath "stupid old man". For some reason in my head I thought this was hilarious. The look of disgust and disappointment that replaced her face was priceless. No idea why I did that, but I still kind of think it was funny. I never told her it was a joke.