I was at WalMart buying my cart load of groceries for the week. The checkout lines were hopelessly full (why don't they put more cashiers out front this time of year!!??) and there was a little old lady behind me who looked like she was really tired. She had about half as much stuff as I did so I let her get in front of me (illiciting some strange looks from people). She was very nice about it and thanked me profusely.
My instant karma? My bill was way lower than I expected and when I came home, hubby had the house straight, laundry folded and floors cleaned.