Which word is best used in place of discontentment to keep the meaning of the sentence the same?

The best word to use in place of “discontentment” is “misery.”

Explanation: “Discontentment” refers to a feeling of dissatisfaction or unhappiness, which aligns closely with “misery.” The other options—potential, sensation, and uncertainty—do not convey the same sense of unhappiness or dissatisfaction.