Any good therapist will tell you that ALL emotions have a purpose. That ALL emotions should be felt. Being happy all the time...being a Pollyanna, it's no way to live life.
Don't have much time to read and write this week, so googling what a Pollyanna is will have to wait.
I might be willing to agree on that all emotions have a purpose, but not all of these purposes are beneficial ones.
Example: What beneficial purposes do emotions have that lead to road rage? Because, frankly, I can't see anything beneficial coming from that.