I was just thinking about this yesterday, without even knowing what it was called. I do long daily walks, in which I see the same people walking about the same

I was just thinking about this yesterday, without even knowing what it was called. I do long daily walks, in which I see the same people walking about the same time. I smile and say hi to everyone I walk past, but not everyone says it back, or even acknowledges me for that matter. I was wondering why I still bother to say hi to people that seem grumpy and don't return the greeting. I said to myself that, just because they're grumpy today, doesn't necessarily mean they're grumpy people, and maybe they'll be less grumpy tomorrow, so I'll just keep greeting them as they pass. It was nice reading about this effect today, as it validated my decision to not give up on them by attributing today's grumpiness to their personality in general.