According to my training, emotions are an automatic, sensory process that occur in our bodies as a reaction to external and internal events. This means that all emotions have causes and therefore cannot be wrong.
DBT (Dialectical Behavioral Therapy) uses the word valid to describe the inherent "rightness" of emotions. People intuitively sense the validity of their emotions and sensory experiences and dislike being told these experiences are wrong (which is called invalidation). An example of invalidation that most people have experienced has to do with temperature, i.e., "how can you be cold when it's so hot in this restaurant?" In this situation, a more accurate (and less invalidating) statement from the other person might be "I'm feeling hot and don't understand how you can feel cold."
"If all emotions are valid," you may be thinking, "why do they cause me so much trouble?" One main reason that emotions can get in our way is that not all emotions are justified. To say an emotions is justified is to say that the emotion, its intensity ,and duration fits the facts of the current situation. An example of a justified emotion would be initially recoiling in fear from a brown recluse you uncovered while cleaning out your closet. An unjustified emotion would be avoiding minestrone soup 10 years after having a bowl that made you sick. It's unlikely that every (or even many!) of those other bowls of minestrone soup would make you sick.
Now, missing out on 10 years of minestrone soup is probably not a huge loss. But what about 10 years of less satisfying relationships? Or 10 years of persistent sadness?
A major part of the way I practice therapy is helping individuals to recognize that while all of their emotions are valid, they may not all be justified. I then help my clients to interact with their unjustified emotions in ways that begin to free them from emotions that are getting in the way of living the life they want.