The main example that really showed this to me from the chapter was talking about a cashier at the grocery store. The have two options when a customer comes up: they can either just rush through the groceries without talking or they can make it more enjoyable by talking, scanning the groceries a fancy way, or just trying to be happy.
There are times not just at work but everyday when we don't feel like doing something. We don't want to talk to others, or do anything. But that is the job of life. That is when the acting comes into place. You aren't trying to cover up how miserable you are, you are just trying to make things more enjoyable and comfortable for others around you.