Some emotions are very similar to others. You might think that serenity is the same as tranquility, but if you explore it more deeply you will find that these are two different notes on the emotional scale. Depression is not quite the same as sadness. Even though they might be in the same general area, these are two different notes. When you explore emotions that are similar to each other, and might be considered to be in the same "family" of emotions, find out what the subtle differences are between them. This can be a very interesting exercise.