Euphoria refers not only to happiness, but also excitement. The excited emotion is actually a surprise emotion, not a happy emotion. Incidentally, on this wheel of emotions, the emotion of "excited" is adjacent to the "joyful" emotion you described, which is a happy emotion. In general, it seems like that the closer an emotion is to another on this wheel, the more similar they are to each other.



More specifically, the emotions "energetic" and "liberated" are next to both each other and the line between surprise and happiness. Accomplishing a goal like becoming lucid can cause one to become energetic, especially if a lot of work went into achieving the goal or if the goal was otherwise difficult to achieve. At the same time, becoming lucid can be liberating because there are usually less restrictions in dreams.