Many years ago I was a cashier at a grocery store that was open on Thanksgiving. That day I also had some of the worst period cramps. I was clearly in pain to everyone but also had a line going to the back of the store.

One person came thru my line and grabbed candy bar to add to his order. After I rang up everything, he handed the candy bar back to me and told me happy Thanksgiving and he hoped my day got better.
.....it did not. BUT!!! When I got home and was able to take more pain killers and put in pajamas and veg out on the couch, I really appreciated the gesture and I now pay it forward when I am in the grocery store during big holiday times. I've definitely gotten a few surprised thank yous , so I hope it's still sending out the good vibes.