When it comes to uplifting one's mood, there are several synonyms that can be used instead of "improve in spirits". One might use the phrase "lift one's spirits" to convey the same sentiment, or use words such as "cheer up" or "brighten". Other options may include "encourage", "motivate", "inspire", "stimulate", or "energize". These words can be used to describe a variety of situations, from a simple conversation with a friend to a motivational speech from a leader. No matter the context, these synonyms can help convey the message of boosting one's mood and overall outlook.