"Grumpy Monkey" by Suzanne Lang
"Jim the chimpanzee is in a terrible mood for no good reason. His friends can't understand it--how can he be in a bad mood when it's SUCH a beautiful day? They encourage him not to hunch, to smile, and to do things that make THEM happy. But Jim can't take all the advice...and has a BIT of a meltdown. Could it be that he just needs a day to feel grumpy?
Suzanne and Max Lang bring hilarity and levity to this very important lesson. This picture book is an excellent case study in the dangers of putting on a happy face and demonstrates to kids that they are allowed to feel their feelings (though they should be careful of hurting others in the process!)."