The antonyms for the phrase "gives a piece of one's mind" could include remaining silent, staying quiet, listening peacefully, and refraining from speaking one's thoughts or feelings. To give a piece of one's mind suggests a sense of confrontation or even anger, so the opposite could be to remain calm, composed and diplomatic. Alternatively, one could choose to express oneself through kindness, empathy or gratitude, as opposed to criticism or reprimand. Rather than attacking the person or problem directly, one could offer solutions or suggestions for improvement. In any case, the antonyms for "giving a piece of one's mind" are actions that demonstrate patience, understanding, and clear communication.