The phrase "breaking one's heart" signifies causing great emotional pain or distress, which is often the result of a betrayal, rejection or loss. Antonyms for this phrase could include "mending one's heart," which implies healing or repairing emotional wounds, and "enriching one's heart," which means filling it with love and joy. Other antonyms could be "supporting one's heart" or "nurturing one's heart," highlighting the importance of proper care and attention to emotional needs. Ultimately, antonyms for "breaking one's heart" emphasize the positive actions and emotions that can bring comfort and happiness to oneself or others, rather than causing pain.