One way to teach this concept is to read the book, Are You Grumpy, Santa? by Gregg and Evan Spiridellis. As I read the book aloud, I paused to allow students to predict the feeling that Santa would have at various events in the book (kinder students made the face of the feeling they predicted). I made sure to point out how Santa's feelings changed from one event to another. By the time we reached the end, students could clearly see how Santa experienced a wide range of emotions, and eventually ended up happy. I asked them if this meant Santa would then remain "happy ever after," and was actually pleased to hear them all say no! They seemed to grasp the idea that it is okay to have a range of feelings and that none will last forever.