When feeling down or unhappy, there are many synonyms for the phrase "low spirit" that can be used instead. Some suggestions include feeling blue, feeling downcast, feeling disheartened, feeling dejected, feeling discouraged, feeling miserable, feeling sorrowful, feeling despondent, feeling crestfallen, feeling unhappy, and feeling melancholic. Each of these phrases can be used to describe a range of negative emotions, from slight sadness to deep despair. It's important to remember that everyone experiences difficult emotions from time to time, and there are many resources available for those who are struggling with their mental health.