Chuck up the sponge is an idiomatic expression that means to give up, surrender, or quit. The antonyms of this phrase include persevere, persist, endure, sustain, continue, persist in, stick with, and keep going. These words all suggest a determination to keep trying or fighting despite obstacles or setbacks. When you persevere, you don't give up in the face of adversity. You're capable of sustaining your efforts over time, even when progress is slow. Endurance suggests strength and stamina, while continuing or sticking with something indicates a commitment to seeing it through to the end.