If this one brings a tear to your eye immediately, it's OK, it did to us, too. This was a letter left, along with a $20 tip, to a waiter in a restaurant from an elderly lady who was eating on her own.
Picture the scene - an old woman eating alone in a restaurant where she would have been easy to ignore whilst staff attend the bigger tables. But Luke made the time to talk to her and make a difference to her day without knowing a single thing about her. There's no way Luke could have known what a deep impact he could be having on this lady just by being polite and courteous, but then that's true of all of us. Each of us interact with people we don't know almost every day. We could be having a bigger impact than we realize every time we have a conversation.