When we want to describe something that boosts our mood and puts us in a positive frame of mind, we often use the phrase "improving spirits." However, there are many other ways we can express this concept, depending on the context and the specific emotions involved.
Some synonyms for "improving spirits" might include "uplifting," "inspiring," "encouraging," "heartening," or "enlivening." If we want to focus on the idea of feeling lighter or more carefree, we might use phrases like "lifting one's mood" or "lightening one's outlook."
Other related terms we might use to describe something that improves our spirits could include "felicitous," "joyful," "exhilarating," or "blissful.