I occasionally read some of these threads where people have huge challenges to deal with on an everyday basis - serious health issues, major family crises, unemployment - - -
So, the occasional clash/rudeness/stupidity one runs into is definitely in the "sand in your shoes" category. Doesn't really hurt one, but it is inconvenient and uncomfortable and ANNOYING!
Stop and dump the sand out, wipe one's feet off, and go on one's way.
Sometimes it is the "little things" though, that can really get our grundies in a big bunch.
Ever hear of the "kick the cat/dog syndrome"?
It's "random acts of kindness" in reverse.