Antonyms for the phrase "cheer someone on" could include "discourage," "dissuade," "dampen," or "undermine." These words suggest a lack of support, enthusiasm, or belief in the person or their endeavors. When someone is discouraged or undermined, it can have a negative impact on their motivation and self-esteem. Conversely, when we cheer someone on, we offer them encouragement, validation, and positivity. Whether it's a friend, family member, or colleague, cheering someone on can help them to feel seen, heard, and valued. By contrast, withholding encouragement or actively undermining someone's goals can have damaging consequences for their success and well-being.