I handle difficult customer interactions with grace. You have to take into consideration that you don't know what that person is going through. Anybody can have a bad day. 99% of the time it's nothing that you've done. It's just a series of events that have made that person feel that way for the day. Sometimes they're just grumpy and you just do what you can. You smile. You be extra polite. Go out of your way to compliment them. Listen. If they want to talk, listen and have empathy.