Put on cloud nine means to feel ecstatic, happy or overjoyed, but the antonyms for the expression are feelings of disappointment, sadness, and depression. When you put someone or yourself down, you lower their self- esteem and make them feel worse about themselves. Another antonym for "put on cloud nine" is grounding, which is a way to bring someone back to earth and reality, to make them think realistically rather than overly dreamy or unrealistic. Other antonyms include feeling discouraged, disheartened, unenthused, and demotivated. It's essential to understand these antonyms to fully appreciate the meaning behind the phrase put on cloud nine.