The phrase "lets sunshine in" is an expression of allowing brightness, positivity, and happiness into a situation, environment or relationship. Antonyms for this phrase would be those that suggest the opposite emotions, such as darkening, blocking, dampening or stifling. These antonyms are often associated with feelings of negativity, sadness or oppression. Examples of such antonyms include phrases like "closes the door on happiness," "buries the light," "puts a lid on optimism," "dulls the glow," "covers the spark," or "obscures the hope." These terms reveal the opposing forces that counteract hope and happiness, emphasizing the importance of staying optimistic and open to positivity.