The phrase "calling quits" refers to ending something or giving up on a project or relationship. Antonyms for this phrase could include words like perseverance, determination, commitment, or resolution. Instead of quitting, one could choose to continue with renewed vigor, persistence, or resolve. Other antonyms might include terms like carrying on, persisting, fighting, or soldiering on. Rather than giving up, people might choose to push forward, even in the face of difficulty or adversity. While quitting might be necessary at times, it is often more rewarding to stick with a challenge and see it through to the end.