It's good to be grateful for people's kindness.
Judy was walking inside a mall, and a man held open a door for her.
Judy wanted to say something to the man.
Judy grins at the man and thanks him for holding the door.
Judy told the man that she can open her own door.
The man feels good for doing something that made Judy smile.
The man feels bad and feels guilty for thinking he would make Judy happy.